[quote=@HellishWaffle]
<Snipped quote by Willy Vereb>

Hm. Could be interesting. Sure why not?
[/quote]Basically Martians landed on the planet but while they conquered a country or two they couldn't advance much further yet and their homeworld lacked resources to send further support thus they're pretty much stuck here and has to make things work.
They have some unique technologies like heat rays (think of searing beam of light akin to Archimedes' mirror or when you use the magnifier on ants except this is generated from a power source) or their weird walkers (though the originals are made of lightweight metal not found on this planet so their mainline walkers are much smaller now). They also adopted a number of technologies from humans and other locals albeit their arrogance still prevents them to embrace it.
Martians also hold whoever is in their country as slaves but aside from that they can be reasoned with and can engage in diplomacy or trade. So you aren't forced to fight them at all costs.