They've adapted the tech found on mars - i recall something like that being implied.
But did they manage to adapt the technology before - or after the first war?

If before (which is what I believe happened):
Why didn't the Martians win the war?

It sounds and looks like all of the flying castles were in earth's orbit for the last 15 years, why exactly do they need a Casus Belli in the first place

If after:
Why did they even go to war against Earth back then? they are (most likely) a relatively small colony compared to Earth's population and depend on its ressources and manpower etc.