Trench

From BoardGameGeek:

Trench is an abstract strategy game for two players based on the trench wars of World War I. Unlike most games, in Trench the 8x8 grid board is diamond-shaped; each player sets up his army on opposing sides of the "trench", which divides the board into two. As hostilities between the armies commanded by the players grow, each attempts to seize control over the trench in order to take full advantage of its strategic potential, hoping thus to breach the opponent's defenses and capture the most valuable and important pieces. From the Soldiers to the General, each piece being subject to specific maneuvers, all will have to cooperate in order to be able to occupy the trench, invade the enemy's territory, and vanquish the foe. The army that manages to survive after two battles wins the game!