The expansion pack titled Sabre Squadron was released during October 19, 2004, in the US, introduced nine new single player missions, seven new multiplayer maps, and a now finished, deathmatch map called "Poland", which had been featured in the game's intro and was titled "London" and available for play in its unfinished state before this release, new weapons: the RPzB 54, the MAS-36, the G43, a suppressed P08 and a Harrington & Richardson Mk VI flare pistol; a co-operative multiplayer mode is also added. Other enhancements such has emptying the lungs while sniping were included along with the access to original Hidden and Dangerous 2 missions through Sabre Squadron's interface.
Source: Wikipedia, "Hidden and Dangerous 2", available under the CC-BY-SA License.