It was the visitors who opened the scoring in the 40th minute as Matt Jarvis nodded home from close range, but the Gunners were level before half time courtesy of a trademark Lukas Podolski strike.
Olivier Giroud then put his side ahead 10 minutes after the restart with a lovely finish from a long ball, while Podolski wrapped up the points with his second of the match 12 minutes from time.
You can read how an absorbing 90 minutes unfolded courtesy of Sports Mole's live minute-by-minute coverage below.
6.45pmGood evening! Thank you very much for joining Sports Mole for tonight's huge Premier League encounter between Arsenal and West Ham United at the Emirates Stadium. The Gunners are in desperate need of a win, but the Hammers have been notoriously difficult to beat of late, so we should be in for an intriguing encounter. Let's start with a look at the hosts...
6.47pmAfter a troubling month, Saturday's victory in the FA Cup semi-final brought some much needed sunshine to Arsenal's increasingly gloomy season. They will now have the chance to finally end that nine-year trophy drought that looms over the club when they face Hull City at Wembley in May but, before that, they have plenty of work to do in the league.
6.49pmA run of four games without a win in the Premier League has left the Gunners fighting for a top four space which is now out of their hands. Shortly before their FA Cup semi-final against Wigan they had been displaced in the Champions League qualifying places by Everton, and they have two points to make up before now and the end of the season if they are to win their spot back from the Toffees.
6.51pmThat will not be easy for Arsenal, however, particularly considering the sensational form Everton are in at the moment. The Gunners are likely to need wins in all five of their remaining matches this season and, while they have the kinder run-in compared to Roberto Martinez's men, their recent record of just three league wins in 11 suggests that they are also more than capable of slipping up before the end of the campaign.
6.53pmAll of that conspires to make tonight's game arguably as important as Saturday's semi-final against Wigan. The debate over whether Arsenal should prioritise silverware or a spot in the top four is intriguing, but Wenger will now be hopeful that he doesn't have to make a choice. With the FA Cup on the back-burner for a while, he can focus his full attention on Premier League matters, starting with what is a must-win game tonight.
6.55pmShould they win tonight then they would move back into the top four, but it could only be for 24 hours as Everton host Crystal Palace tomorrow night - a game you'd expect the Toffees to win even considering Palace's recent good form. However, while their struggles to reach the top four suggests a below-par season, they are in fact four points better off than at the same stage last year. On that occasion, they clinched Champions League qualification on the final day of the season.
6.57pmThe fact that the majority of their five remaining games will come at the Emirates could prove to be a pivotal factor in the race for fourth. The Gunners are unbeaten at home in the Premier League since that dismal loss to Aston Villa on the opening day of the season, a run of 15 matches. Indeed, that Villa loss is their only league defeat at home in their last 25 games in front of their own fans, a run that stretches back over a year to January 2013. In all competitions, only European champions Bayern Munich have beaten Arsenal here since October.
6.59pmHowever, their last two games here have ended in draws, and a similar result tonight would make it five league games without a win for the Gunners - something they haven't endured since 2009. They do have a good record in London derbies this season, though, picking up 22 points against fellow clubs from the capital - a tally that no other team in the league can beat.
7.01pmWest Ham have had a certain amount of joy in London themselves, though. They have already won twice in North London this season, beating Tottenham Hotspur 3-0 at White Hart Lane in the league and then again 2-1 in the League Cup. They also held Chelsea to a goalless draw at Stamford Bridge and could well look to employ similar tactics to stop Arsenal tonight.
7.03pmThey come into the match in decent form, with six wins in their last 10 games propelling them away from danger and fighting for a place in the top half. They are now six points behind 10th-placed Stoke with a game in hand, which is a far cry from the situation they found themselves in ahead of the reverse fixture against Arsenal on Boxing Day. They were amongst the favourites for the drop then, and it is testament to the work that Sam Allardyce has done that the threat of relegation is now only a mathematical, rather than a realistic, one.
7.05pmEven the matches they haven't won will give them a bit of confidence, particularly their last outing against league leaders Liverpool. The Hammers tested Brendan Rodgers's side and eventually fell to a narrow 2-1 defeat in controversial circumstances. It was the latest example of how Allardyce can make things tough for the bigger teams in the league, and Arsenal will certainly not be expecting an easy ride tonight.
7.07pmOne thing that does play into West Ham's hands is that they have had nine days off going into this match. That would give most sides an advantage whatever the circumstances but, considering an injury-depleted Arsenal side played 120 minutes plus penalties on the notoriously energy-sapping Wembley surface just three days ago, it could be a crucial factor in tonight's encounter.
7.09pmDefensive solidity has been the key for the Hammers' journey up the table since the turn of the year, and they are likely to go into tonight's match with a clean sheet as their number one priority. They have certainly shown that they are capable of that, having kept the opposition at bay on 13 occasions already this season - only Chelsea have kept more clean sheets. However, they aren't quite as good when they take the lead in games having dropped 17 points from winning positions, second only to Southampton this season.
7.11pmIncidentally, they have taken the lead in their last three matches against Arsenal, but have gone on to lose each and every one of them. Away from home they have picked up enough points to survive but have struggled to find any sort of inconsistency. In fact, this evening they are bidding to win back-to-back away games in the Premier League for the first time since December 2007.
7.13pmA draw against Chelsea and victory against Tottenham are highly respectable results for the Hammers, but they have generally struggled against the top teams this season - at least in terms of results. The win over Spurs is their solitary success against any of the current top seven in the table, and another victory in North London tonight looks unlikely.
7.15pmTEAM NEWS: Right, the teams are in and the big news for Arsenal is that Laurent Koscielny has been passed fit to play. He comes into the middle, with Vermaelen moving to left-back in place of the injured Nacho Monreal. Tomas Rosicky, Olivier Giroud and Wojciech Szczesny also return to the starting lineup, alongside the incoming Kim Kallstrom. West Ham, meanwhile,a re without Kevin Nolan after he failed a late fitness test, while Collins and O'Brien are also not fit enough. Full teams news for both sides coming right up...
7.19pmWEST HAM SUBS: McCartney, Vaz Te, Taylor, Jaaskelainen, C Cole, J Cole, Johnson
7.21pmSo, what can we make of those two teams? Well, it is a big boost for Arsenal to have Koscielny back at the heart of the defence as he has forged a very good partnership with Mertesacker this season. His inclusion means that Vermaelen edges out to left-back, replacing Monreal, who picked up an injury in the FA Cup semi-final. Gibbs, who came on in that match, doesn't even make the bench as he continues recovery from an injury of his own.
7.23pmLukas Fabianski could be forgiven for feeling a bit miffed at being dropped to the bench following his heroics in the penalty shootout on Saturday, but Wenger was always expected to recall Szczesny for such a big league game. The Pole is Arsenal's usual number one and, while Fabianski did play a major part in their FA Cup success at the weekend, there is no time for sentiment at this stage of the season with so much to fight for.
7.25pmWenger has made a few changes in midfield after such a gruelling game against Wigan. Ramsey drops to the bench having played almost the full 120 minutes on his first start since the reverse fixture between these two on Boxing Day, while Oxlade-Chamberlain is also left out of the starting XI having suffered with cramp in the closing stages of Saturday's game. The returning Rosicky eases Arsenal's injury woes in midfield somewhat, while there is also a rare start for Kallstrom.
7.27pmUp front, it is once again the expected change as Giroud comes back into the starting lineup to replace Yaya Sanogo. Giroud came off the bench at Wembley but would be the fresher of the two strikers after Sanogo did a lot of running throughout the game. He showed aspects of play that Giroud lacked in the match - such as pace - but his finished was poor. Giroud hasn't been in the best form of late, but there is no doubt that he knows where the goal is and he will fancy his chances of getting on the scoresheet tonight.
7.29pmAndy Carroll may also fancy his chances of scoring tonight given how many problems he caused Liverpool in the last match. His aerial prowess is well known now and the likes of Koscielny and Mertesacker will have a tough task on their hands dealing with him this evening. The Hammers are likely to pump plenty of high balls into the area and Carroll will always win his fair share of them, so expect a few chances to come via that route today.
7.31pmOne big blow for the Hammers is the absence of Kevin Nolan, however. He is an expert at linking up with Carroll and latching on to the second balls in and around the penalty area. Downing and Jarvis will still look to provide the team with width and crosses into the area, but it will be up to Diame to fill in for Nolan and pose a goal threat from midfield.
7.33pmDefensively, West Ham have struggled with injuries this season but have still managed to keep things pretty tight at the back most of the time. The absence of Collins is a blow for Allardyce's side, but Tomkins and Reid have played plenty of football this year and will know exactly what their jobs are tonight. Having had nine days to prepare for this game, you can be sure that the defensive unit will be well organised tonight.
7.35pmPREDICTION: Right, we're 10 minutes from kickoff in North London, which means that it is time for my prediction! The Gunners were not convincing against Wigan on Saturday, despite their win on penalties, and it has been a long time since they were at their best in the league. However, they have generally been good at home this season and simply have to win this match, while West Ham have relatively little to fight for. The visitors won;t make it easy for Arsene Wenger's side, but I'm going for a 2-0 home victory.
7.37pmAny such result would keep up Arsenal's impressive recent record against West Ham. They have won their last six meetings with the Hammers in the league and are unbeaten in their last 12 in all competitions - a run that stretches back to when Bobby Zamora gave his side a 1-0 victory at the Emirates seven years ago. The Gunners tend to score quite a few past West Ham too, netting 14 times in their last four meetings.
7.39pmThe first goal tends to be pretty important in Arsenal matches - they have earned the most points (55) from games in which they have opened the scoring this season, while they have won just one of the 12 games in which they have conceded first. Incidentally, that solitary victory came in the reverse fixture against the Hammers.
7.41pmEvery match from now until the end of the season could reasonable be termed Arsenal's biggest of the campaign given their current predicament. This is a match that they would really be expected to get maximum points from, and failure to do so would really hand Everton the initiative. If Arsenal were to fail to win tonight and the Toffees bear Crystal Palace tomorrow, it could well spell the end of the Gunners' Champions League hopes.
7.43pmBefore kickoff we will have a minute of silence in memory of the Hillsborough tragedy, which occurred exactly 25 years ago today.
1 minKICKOFF: West Ham get us underway at the Emirates, which is by no means full at the moment. There are plenty of empty spaces around the place, which is surprising considering how big a match it is for the hosts. No doubt the fact that it falls on a Tuesday is part of the reason.
2 minArsenal start the match well and win an early corner, which West Ham can only clear as far as the edge of the box. Rosicky attempts an ambitious first-time volley, but his effort loops easily into the arms of Adrian.
4 minAs expected, Arsenal are controlling the ball in the early stages as they knock it about patiently. They will want to tire West Ham as much as they can today considering their own exploits just three days ago.
5 minDiame weaves his way past a couple of challenges to make his way into the box before opening his body up and looking for the far corner. Mertesacker is well placed to make the block, however, and the danger is cleared.
7 minWest Ham are pressing quite a lot in these early stages now and they almost create a good chance down the left as Armero's throw finds Diame in an advanced position. He clips a good cross into a dangerous area, but Nocerino's shot from a tight angle is blocked.
9 minIt has been a very good start from the visitors here. Arsenal appeared to have settled quickly, but West Ham are now asking the questions in an attacking sense, with Diame in particular finding plenty of space in advanced positions. The Gunners need to attend to that problem sooner rather than later.
11 minWest Ham win a free kick in a decent position to load the box, but Arsenal just about deal with the danger after a bit of head tennis. Arsenal then break quickly through Rosicky, but his attempted crossfield pass to Cazorla was off target.
13 minStill no chances to speak of for either side so far, but Arsenal are beginning to see more of the ball. However, they are trying an unusual amount of long balls forward and they simply aren't working at the moment.
14 minCLOSE! Almost a great chance for the Gunners to take the lead as the ball is worked out to Podolski on the left flank. He flashes the ball across the face of goal that Giroud is inches away from connecting with at the front post. He got there in time, but just seemed to misjudge it.
15 minYELLOW CARD! The first card of the match goes to Rosicky for a poor challenge on Armero. No complaints there.
16 minJarvis deserves a lot of credit there. He beats Sagna to the ball inside the box and the Arsenal right-back comes swinging in with his leg and makes contact with the winger. However, Jarvis doesn't go down when so many other players would have, instead recycling the ball and creating a chance for Carroll to nod a header over the top.
18 minGood play from Jarvis as he gets a yard on the left before sending a fine cross towards the back post that Carroll is very interested in. He throws himself at the ball, but Mertesacker gets there first to put it behind for a corner.
19 minCHANCE! Big chance for the Hammers! The resulting corner is collected at the back post by Carroll, who rather scuffs his cross back into the area. However, the ball rolls to Diame, who has a bit of space on the edge of the six-yard box. He rushes his shot, though, sending it way over the bar when he really should have done better. That's the best opening of the game so far.
21 minWest Ham have been the better team in this opening 20 minutes, asking more of the questions in the final third. Arsenal do appear to be suffering something of an FA Cup hangover as their performance is very flat at the moment.
23 minArsenal just have not got going at all here yet. The crowd has shown signs of getting a little restless already, and that will only worsen if things stay like this for much longer. This is a must-win game for the Gunners but, so far, they have shown no signs of being able to break the Hammers down.
25 minYou can tell that Arsenal played 120 minutes on Saturday. They have been laboured and slow with their passing, and even defensively they are allowing West Ham too much space in certain areas. There is not much you can do to counter fatigue, so it will be interesting to see how the Gunners cope with this.
27 minSo far so good for West Ham, then. They are playing this game at their own pace, slowing the ball down from restarts and preventing Arsenal from getting any sort of momentum - not that the hosts are threatening to do so. It is all far too comfortable for the Hammers at the moment.
29 minA hint of an opening for Arsenal as Podolski clips a hanging ball into the area that Rosicky attacks. He is beaten in the air and the ball almost falls to Giroud inside the box, but it is just about cleared.
30 minCHANCE! What a chance for Arsenal! West Ham carelessly give the ball away and the ball is slipped through by Cazorla to Giroud, who is deemed to be onside by the linesman. The Frenchman only has the keeper to beat, but for some bizarre reason he tries to flick the ball over the keeper with the outside of his left foot. It is a poor attempt and Adrian makes the save. Terrible from Giroud.
32 minArsenal are starting to threaten more often now. They come forward again here and Giroud pokes the ball towards Rosicky, who has made a late burst into the box. However, he just can't take it in his stride and West Ham eventual scramble it clear.
34 minSuddenly, it is all Arsenal. They have come to life in these last few minutes and are now knocking the ball about at a much quicker pace and in more dangerous areas. The West Ham defence is just about coping at the moment, but the pressure is beginning to build.
36 minNow West Ham begin to threaten again as Jarvis races down the left with Sagna out of position. However, his cross is poor and easily cleared by the hosts, who then launch an attack of their own.
37 minYELLOW CARD! Nocerino is the second man in the referee's notebook tonight having pulled Giroud back on the halfway line. It is perhaps a soft one, but Kevin Friend viewed it is a cynical foul.
40 minWest Ham take the lead at the Emirates! It is lazy defending from Kallstrom as he lets Nocerino run behind him and into the box. The West Ham man forces a save from Szczesny at the front post before poking the ball back into the danger area, where Jarvis is waiting to nod home from close range, It is an untidy goal, but West Ham won't care at all!
42 minWest Ham have now taken the lead against Arsenal in their last four meetings. They have gone on to lose the previous three, but with Arsenal having such a poor record when conceding the first goal and looking sluggish tonight, the Hammers will be confident of holding out here.
43 minSAVE! The Gunners look to find a response before the break as Kallstrom, who let Nocerino go in the build-up to the goal, hammers a powerful strike towards the front post. It is a well-struck shot, but the Swede was always going to struggle to beat Adrian from there, and indeed the shot is saved.
44 minThere is the response! Arsenal get the equaliser before the break as Downing gives the ball to Cazorla away with a poor clearance from his own corner. The Spaniard then slips a lovely pass through to Podolski down the left channel, and he drills it into the opposite corner with a trademark finish. Big goal for Arsenal, that.
45 minThere will be two minutes of added time at the end of this first half.
8.38pmSo, we go into the break all square after two goals in the final five minutes of the first half. Arsenal showed good character to come back from a goal down when not at their best, but they still need to find another goal in the second half if they are to end the day in the Champions League qualifying places. West Ham will be happy with their performance overall but unhappy that they weren't able to hold onto their lead until at least half time.
8.40pmThe opening goal of the game came in the 40th minute as Nocerino was allowed to run into the box by Kallstrom before eventually poking the ball across to Jarvis, who nodded in from close range. It was a very messy goal and there was an element of luck about it, but the Hammers had threatened enough to warrant their lead.
8.42pmThe Gunners managed to get the equaliser just before the break, however, and it could prove to be a crucial goal for them in the race for fourth place. After an uninspiring first-half display, they were handed a chance when Downing's poor clearance went straight to Cazorla. The Spanish midfielder then showed his class with a lovely pass into Podolski, who found the bottom corner with an accurate finish from the left channel. He has scored many goals just like that in his career, but if Arsenal go on to win this match then it could be one of his most important in his time with the club.
8.44pmThe performance from Arsenal made that equaliser all the more important. They hadn't really looked like threatening the West Ham defence and certainly seemed to be suffering from fatigue following Saturday's FA Cup semi-final. However, that goal completely changed the atmosphere inside the stadium and could give the players a bit of momentum for the second half.
8.46pmDespite not being at their best, the clearest chance of the match - other than the goals - has fallen to Arsenal. Cazorla was once again the provider as he threaded the ball through to Giroud, but the striker attempted a highly ambitious and bizarre finish that Adrian saved.
46 minKICKOFF: The Gunners get us back underway for the second half, and what a big 45 minutes it is for them. They need a win to move back into fourth, but you feel that they also need to improve on that first-half performance to pick up all three points.
47 minSHOT! Arsenal look to apply some early pressure, but the first shot of the half comes from West Ham as Downing leads a counter-attack down the right flank. He cuts onto his left foot before dragging an effort wide of the near post.
49 minDiame leads another West Ham attacks as he cruises past Arteta in midfield before getting into shooting range. He lines up a shot from around 25 yards out, but his effort flies a long, long way over the crossbar.
51 minWinston Reid is limping a bit at the moment following a challenge from Cazorla. He has had a torrid time with injuries already this season, so Allardyce will be hoping that this is nothing serious. It doesn't look like it is.
52 minA blocked Downing cross falls to Nocerino, who just guides a clever cross in towards a gaping space in the Arsenal box. Carroll is just on his heels, however, and can't latch on to it as it runs through to the keeper.
54 minGood defending from James Tomkins as he cuts the ball out at the front post following a quick low ball in from Podolski. It just skewed off his boot and could have gone anywhere, so he will be relieved that it flew over his own bar rather than under it.
55 minWhat a superb goal that is from Giroud! An Arsenal corner comes to nothing, but the ball is pumped back into the box by Vermaelen. Giroud shows good strength to hold off Reid, who puts in a rather weak attempt to stop the striker. He then produces one of the most delightful pieces of control you will see this season before firing the ball past Adrian with his second touch. Great touch, clinical finish.
57 minReid has to look at himself for that goal. It almost looked like he assumed the ball would go out and so made no real attempt to cut it out or stop Giroud getting to it. He was punished for the misjudgement, but take nothing away from Giroud touch and finish, especially considering his earlier miss.
59 minThe atmosphere has changed inside the stadium now and Arsenal's players are beginning to respond on the field. They are starting to gain more control over proceedings and could fancy their chances of getting more. Goal difference could well play a part in the race for fourth, and they are currently behind Everton on that front too.
60 minYELLOW CARD! Armero brings down Giroud on the edge of the box, but the referee flashes the card to Diame for dissent having given the free kick. Arsenal now have a free kick in a good position, particularly with the left foot of Poloski.
62 minSAVE! It is indeed Podolski who takes on the duties, curling an effort towards the goalkeeper's side rather than going over the wall. Adrian had started going over towards his left a tiny amount, but he was still able to make a comfortable save, parrying the ball to safety.
63 minYELLOW CARD! Kim Kallstrom is the latest player in the book, and he can have no complaints as he scythed down Nocerino on the halfway line.
64 minCLOSE! So close to an Arsenal third as Cazorla latches on to a long crossfield pass to launch a counter-attack. The Spaniard cuts inside onto his left foot and is afford far too much time and space on the edge of the box to send a swerving shot whistling past the post. That was just a whisker wide, and Adrian was not getting there.
66 minArsenal have had the better of this match since their second goal, and West Ham are now struggling to make any headway in the final third. The Gunners have settled now after a nervy first hour or so and it would be a surprise if they didn't end up winning this match.
68 minWenger must be starting to think of substitutions now. His side have a decent degree of control over the game and a number of the players out there played 120 minutes just three days ago.
70 minWest Ham are being limited to half chances now. One such attempt sees Armero lift the ball into the box for Carroll to attack, but he is a long way from goal and can only glance his header wide.
72 minARSENAL SUB: The first change of the night sees Aaron Ramsey come on for Rosicky, who himself is only just returning from injury. Ramsey picked up his lengthy injury in the reverse fixture between these two sides on Boxing Day.
74 minAs things stand, Arsenal will be moving back into the top four at the expense of Everton this evening. However, the Toffees do play Palace tomorrow so it could only be a 24-hour stint in the Champions League places for the Gunners.
76 minSHOT! Arsenal come forward through Giroud, who slips the ball to Ramsey around 25 yards from goal. The space opens up for the sub and he duly lets fly from range, but his effort flies over the top and wide.
78 minFor the second time this season, Arsenal come from a goal down to lead West Ham 3-1. That is exactly what they needed for the last 10 minutes or so as Giroud clips the ball to the edge of the box for Ramsey to cushion a header into the path of Podolski, who lashes the ball past Adrian from close range. He was never going to miss that.
80 minWEST HAM SUBS: The visitors make two changes immediately after the goal, with Ricardo Vaz Te and Joe Cole coming on for Stewart Downing and Matt Jarvis.
82 minThat third goal makes life a whole lot easier for Arsenal in the closing stages of this match. They now have a nice cushion to fall back on and will not be forced to push for anything extra with what must be a tiring side. Certainly, they would have taken this if you'd have offered it to them at half time. They have been much better after the break.
84 minWEST HAM SUB: The Hammers make their third and final change as Andy Carroll makes way to be replaced by Carlton Cole for the final six minutes or so.
86 minHalf an opening for the Hammers as Carlton Cole rises highest inside the area to meet a free kick, but he can only steer his header quite a way wide of the post.
88 minARSENAL SUB: The Gunners make a late change of their own as Santi Cazorla goes off to a great reception to be replaced by Carl Jenkinson. Cazorla has had a good game tonight.
90+1 minThere will be four added minutes at the end of this match, but it has been over as a contest since Arsenal scored their third.
90+2 minArsenal come forward in search of a fourth and Ramsey looks to get it with a turn on the edge of the box and left-footed shot that is comfortably held by Adrian. He did well to create the space to shoot, but the end product was too weak to trouble the keeper.
90+4 minThis game has very much fizzled out in the closing stages, and that is demonstrated by a Nocerino attempt here as he volleys his shot well off target when the ball sat up invitingly.
9.41pmWhat a big win that is for Arsenal. They needed to come from a goal down and it wasn't all plain sailing, but they move back into the top four courtesy of their first league victory in a month. That piles the pressure on Everton now as the Toffees play their game in hand against Crystal Palace tomorrow night looking to keep up their remarkable recent record and regain fourth place. Tonight was a must-win game for Arsenal, though, and they duly obliged with a spirited victory.
9.43pmIt is the fourth time in a row that Arsenal have come from behind to beat West Ham. The visitors took the lead in the 40th minute when Matt Jarvis nodded the ball over the line from close range after a mini-scramble in the area, but Arsenal were level before the break courtesy of a trademark Lukas Podolski finish. Giroud then put his side ahead in the second half with a lovely piece of control and finish before Podolski got his second of the match to seal all three points.
9.45pmRight, that is all we have time for this evening! Thanks very much for joining Sports Mole on what was a big day in the race for fourth place as the Gunners move back into the Champions League places courtesy of a 3-1 win over West Ham. I will leave you with our match report and be sure to stick around for reaction and analysis, which will be on site shortly. There are two more Premier League games tomorrow, so be sure to sheck back in for our coverage of those! Until then, though, it is goodbye from me!