Wars are won on resolve, and mercenaries don't have any. The reason so many of these people fled to Europe in the first place was to avoid getting caught up in violence. They have zero reason to fight anything except the insistence that they fight.

Also, this is racist as hell, why isn't it flagged to death yet?

That's the traditional recipe for military coups. When the ones with the weapons, training, and combat experience have no particular loyalty to the regime, they often start thinking that they would be more qualified to rule.

> If things are as the governments claim

Leaving aside your xenophobic ramblings, that's a VERY BIG "if".

Simply because all bets are off when they come back armed, trained, hardened and angry.