It was first released as Shin Sangokumusou 3 (Japanese: 真・三國無双3) on PlayStation 2 in Japan on February 27, 2003, in North America on March 25, 2003 and PAL version on June 27, 2003. The game was later ported to Xbox on September 4, 2003 in Japan, September 30, 2003 in North America and November 14, 2003 for PAL version.
An example - Xiahou Dun has a lot of LP with Zhen Ji (akin to sleeping with your boss' son's wife, but that's not the point here), and his army is running into some trouble at Chang Ban Bridge. At this critical moment, Zhen Ji will announce herself and appear from an allied stronghold to help Xiahou Dun. These walk-on appearances by the guest officer will place the officer in Follow/Attack Mode like a bodyguard, but the officer will not heal like your bodyguards (see below) and if killed, will affect your morale as if an allied officer was routed/slain. However, the double musou attack (when two officers' musou meters are max and musou is used simultaneously) can be used with this officer. It's the next best thing to having a human buddy help you (and the fog is much reduced).