Request for help with campaign I'm building

[Suhiir]

When I have the time/inclination I've been working on a campaign featuring a battalion size Marine Expeditionary Unit (the "standard" independent USMC fast reaction force stationed aboard ships worldwide). I'd initially intended it to be an Iraqi civil war campaign, but the recent events in the area involving ISIS (or ISIL or DAESH or IS) have caused me to reconsider.

Given that ISIS has basically declared war on the entire world I think this could lead to something akin to the coalition of Austria-Hungary, France, Germany, Italy, Japan, Russia, United Kingdom, and the United States that opposed the Boxers in China between 1899 and 1901.

The basic premise would be that the MEU has been deployed to Baghdad to safeguard the various international interests, then ISIS stages a coup that has a lot more popular support then anyone expected. The various national embassy's, with their guard detachments, all band together to fight their way to the coast (or Saudi Arabia) since while seizing an airfield would be doable overflying the area to get in and out of it would be problematic.

So sort of a modern Chosin Reservoir type campaign.

What I could really use is some idea what sort of forces the various international communities would deploy to protect their embassy in potentially hostile nation. And which nations would be likely to evacuate all but a skeleton staff in the face of potential uprisings.
Due to the 500 unit limit in campaigns I'd need to limit each security force to a less then company sized formation.

Suggestions/help from those of you that live in various parts of the world would be appreciated.