Russia and the US recently completed a command post exercise in which simulated US and Russian forces conducting a joint operation were threatened by ballistic missiles from a common enemy. The US employed Patriot-PAC3 in defense while the Russian forces deployed S300s. The two defense systems performed in an "independent but coordinated manner". Basically, the two exchanged information from satellites and other warning systems, and arranged in advance which defensive missile batteries would cover which areas. The next joint exercise will be held in Jan 2002 and will focus on communications and datalinks to improve coordination.--Stephen V Cole