Former Porto duo Mangala and Fernando cost £32m and £12m respectively, but Kompany has insisted that reinforcements in defence and midfield were needed to compensate for the departures of Joleon Lescott and Javi Garcia.
Kompany told reporters: "The summer reinforcements? People should see that as logical for a team like us, to get reinforcements every year.
"We are forced to. That is a fact. Joleon Lescott is leaving? We must get reinforcements for that position. Javi Garcia is leaving us? We have to add a player in that position."