I actually think the enemy here maybe terrorist, like from ISIS or example.Wait, this game is set in the UK? I always thought that devs wanted to just sorta keep where the game was set ambiguous (though I also felt like it was some sort of first world country that was a former British colony like Canada or Australia, but much less important). I feel like this makes sense, because of the inclusion of the Indian girl and because the government has a sort of 'nanny state' mentality.
As for the war, it was definitely not with some major power due to how nuclear weapons have effected war. If I had to guess I would say that they probably got wrapped up in the war on terror, though given how Chang's age is left ambiguous (if I remember correctly) it could have been something from longer ago, like Vietnam or even Korea or Malaysia. Maybe they just intervened in one of the smaller wars in the pacific that people never talked about (keep in mind I say this while taking the position that the country that the game is set in is most likely supposed to be similar to Australia or New Zealand).
Then again, this is all just a silly porn game that I probably shouldn't be wasting time ranting about.
Edit: Also, I don't think Mycock being in bed with the Russian ambassador was supposed to be a message that the country the game is set in is allies with Russia. I think that line's just in there to show how powerful and connected Mycock is.
Since Chang is Asian, it's unlikely she wanted to do experiments on Asian soilders, and Asian is actually far away from UK's conflict of interest.
And it's definitely not America or Europe, because Charolotte is American while Emily is claimed to be a nudist from East Europe, and UK has just quitted the sort of "Human Right Act" according to Maxine's story arc.
What surprised me is that Mycock(Mykock) is actually connected to Russian agents because Russian is often sterotyped as the antangonist after the cold war, but I think it makes more sense if Russia is behind all the conspiracy part here.