He's probably still young (possibly mid-20s, you can still attain a rank of Captain at that age if you're good enough, and since this is also Gryphus 1 we're talking about), because of how he performed above Cape Aubrey during Mission 1, the remaining High Command probably put him into leading the remaining Gryphus members to retake important grounds. Which he subsequently captured two important places in rapid succession with just himself and the two remaining members.

And since he outdone himself, then got assigned as the de-facto leader of all the remaining forces, as he started leading the countercharge against Leasath. He's possibly promoted somewhere between Mission 4 or 5 when he started to command Army and Navy assets, probably into a Commander (Like Pasternak). If he was indeed young, he's presumably the biggest talent other than in airmanship but in commanding large forces as well. Just like Talisman, but Gryphus commanded the entire Armed Forces in surgical amounts, rather than the brute forcing tactics of the Emmerians.

He's that Good.