It was pretty clear for Japanese people and expert translators which is what matters, here's what Sandman said:
About 戦力, yeah, it basically means military strength.
For example, Admirals were referred to as the supreme force (最高戦力) in Marines/WG.
If Kaido wanted to talk about his own strength, he would have used the word "世界一の戦闘力" instead of "世界一の戦力".
people just like to use translations by novice translators to support their own views.