This guy is attacking a colony from a camp. It was an outpost at first. But then it was razed to a camp during the attack. Can he recall his units back to the camp, preventing the attack? Or does Battle Dawn make you follow through with the attack?

he can recall his units back to the camp, but then he can't send any attacks from the camp anymore till he move his units to another OP

and razing the op while he's attacking will not recall the units, he can recall it manually but the game won't force to recall it. the attack still go on as usual

Thank you. This guy is saying he can't recall his attack. And that its glitched or something. But I don't believe him.

there is one possibility

he was in ur alliance, he attacked the op from ur colony
the op got razed, and he returned his units
he left / was kicked from ur alliance
the returned units turned to hostile

guy is fooling around with you, tell him turn back or crush him.

He's bs'ing you

Ask for photo proof.