AFAIK there's not been a case where a military has aided a native population against a vionlently aggressive horde of genetically engineered specimens designed for war.
Well eugenics is simply evolution continued on to it's logical conclusion, namely, we are the greatest. So when Germany attempted to take over the world in WWII (and did a damn good job of it too), they weren't allowed to retreat since 500 German soldiers were obviously better than 5000 inferior, raging slavs.
Turns out Hitler was wrong, the Germans weren't the top of the evolutionary ladder. At least not quite as far up as he liked to think, so of course the inferior slavs smashed them.
However, Britain did interfere on behalf of France in the war, to the point of landing soldiers in France itself. So, to point, they aide a native population against a violently aggressive horde of specimens trained for war and thought to be genetically superior. The USA also interfered in that war on behalf of Britain, but they didn't land there since Britain held out long enough, and Hitler was too ditzy to attack properly after he fired his generals, so they lasted the war. Fairly sure they've gone to Africa though, and NATO went to.. Where was it, up in the European states.. Serbia was in it, Bosnia? Something like that, NATO forces, although not under that name, were Russia, Britain, USA and.. A few others. Can't remember. But that was intervening on behalf of the native populace against a horde of.. Well that's the fun part. Court defense's nowadays often revolve around a psychological state or genetics. It wasn't my fault, my genes made me do it thus it's discrimination if I get sent to jail. A few scientists are even attempting to prove that it's not that we just decide to be bastards, we're actually forced to do it. In which case it was against genetically differing specimens which needed to be put down. They obviously thought that defense through..
Still, that's several cases where on state has intervened on behalf of another. In times of great distress politics matters a tad less. Not completely, but it becomes background to the main fight.
you'll see a lot of very fat well-fed specimens before armed frenchmen are tolerated on British soil.
And that's why the French Foreign Legion exists.
Besides, the original natives of the isles are all dead and gone, bar the Welsh. The only reason you're not French is that they get way too distracted with their hair. Could still happen.
Let's just call everything a gun.
Rifle