As Esli mentioned in the comments on this post,
In an interesting twist, our allies, the Atropians, are role played by OPFOR from 11th ACR, and actually roll in the same equipment as our common Donovian enemy. So the OPFOR not only fight us, but they fight each other.
It’s simply a fact of life that US units will operate alongside allies and coalition partner nations. The only truly unilateral action since before World War II that I can recall is Grenada.
As fractious as the US/British alliance was during World War II, in fact, it was a model of successful allied operations. Very few armies in history can claim such a level of cooperation and success. And since that time, the US and Britain have often operated side by side. Other notably successful partnerships include Australia, and Canada. Non commonwealth nations that we have close relationships with include counties such as South Korea, where for 63 years, Americans and South Koreans have served side by side.
The biggest, most obvious example of allied interoperability is, of course, the NATO alliance, one so successful, it never had to fight to fulfill its original mission.
While the US has a good track record working with several friendly nations, the fact is, most actual combat alliances are extemporaneous. And while other nations may well be willing to fight alongside us in any number of campaigns, it important to remember that they do so for their own reasons, not ours.
Aside from describing how our nation anticipates winning campaigns, doctrine exists primarily to provide a shared vision of how wars will be fought. Every battalion and Brigade Combat Team in our Army fights under the same doctrine. When units that have never trained together before are thrust into combat together, they still have a great deal of interoperability built in due to a single doctrine. But our allies in any given battle may have their own doctrine. And their own political objectives, as well. And few things are more likely to enhance the fog of war than divergent goals.
Battles make strange bedfellows. Don’t forget, Syria sent two armored divisions to fight alongside against Iraq during Desert Storm. Whether Syria genuinely wished to thwart Iraqi territorial ambitions, or just wanted to bask in the goodwill of other coalition nations, for whatever reason, a nation with historical enmity to the US, equipped as a vassal state of the Soviet Union, found itself fighting alongside the US, Britain, France and other nations that have historically been considered its foes.
Command of foreign forces is always more nominal than real. Just as we shudder that the thought of US forces under the command of a foreigner, so to would any ally. Further, no matter what the putative chain of command is for an operation, allies are still sovereign forces, answerable to their own government. Further, it is a very rare foreign force that shares our current doctrine of Unified Land Operations.
So while theoretically, the OpFor in the Greywolves rotation was a net positive in the available combat power, differences in national goals, doctrine, and sheer bloody-mindedness can see a foreign force taking actions that can catch a US commander of guard. Foreign forces may not attack with the zeal US commanders are accustomed to. Or they may actually attack so fast as to find themselves far from support of US forces, and vulnerable to local counterattacks. Or maybe their attention to the laws of war and treatment of prisoners isn’t as fastidious as our own.
US commanders will have to learn to operate alongside foreign troops that vary wildly in their equipment, training, doctrine, support for the rule of law, and ability to operate on a decisive battlefield.
Now for the first time, US leaders are being exposed to the challenges of this in training, rather than having to devise solutions while actually upon the field of battle.