Honestly speaking, the commander of the Army invasion force - Bertrand - is actually fairly competent here. With what he does know is possible, he reacts quite carefully. He sees the land terrain and how it's ambush central with the tall grass and wants their wyvern support to aid in scouting and protecting his forces. When the JSDF wrecks the shit out of their land tortoises, and his subordinate is like "Shit yeah! Let's chase after him!" he's like, "No, you moron. They killed literally every single one of our tortoises, we're falling back. If we chased after them we'd just be playing into their hands."
I mean... the guy was going to lose regardless of even if he was the most brilliant tactician to ever walk on two feet... You just aren't going to bridge that technology gap with no amount of clever tactics and lateral thinking. But given what little he knew and how little intelligence was provided to him, the guy was extremely competent. Much more so than virtually every other high ranking military officer we've seen go against the Japanese.