Skirmish is an online team objective game mode in Resistance 2. It did not feature in Resistance: Fall of Man and was introduced only in Resistance 2 upon launch. It was initially thought of as a replacement for Meltdown, incorporating aspects of the objective game mode although adds additional "objectives" for teams. Unlike any other game mode it is heavily squad based, with teams relying on individual squads of players to complete objectives whilst fighting other rival squads in order to gain points for their team. 

Resistance Multiplayer Game Modes
Resistance: Fall of Man Deathmatch | Team Deathmatch | Capture the Flag | Meltdown | Assault | Breach | Skirmish
Resistance 2 Deathmatch | Team Deathmatch | Core Control | Meltdown | Skirmish
Resistance: Retribution Deathmatch | Team Deathmatch | Containment | Capture the Flag | Assimilation
Resistance 3 Team Deathmatch | Chain Reaction | Deathmatch | Breach | Capture the Flag | War Games | Invasion
Resistance: Burning Skies Deathmatch | Team Deathmatch | Survival