Towards the end of the second age, Osgiliath (the citadel of stars)was built by the Dunedain of Gondor as the capital og Gondor. However during the year 1437 of the third age, civil war broke out in Gondor and it's Dome of Stars, which once housed a palantir, was destroyed. After the plague of 1636, the royal court was moved to Minas Arnor(Tower of the sun), which was later renamed Minas Tirith (Tower of the guard). Once more strife took it and in 4275 Uruk Hai legions from Mordor completly sacked it and the great stone bridge was broken.
Shortly before the war of the ring, Boromir, Captain of the white tower and eldest son of Denethor, steward of Gondor retook the city with the help of his younger brother, Faramir. Although it was fortified, little was made to make it habitable once more.
In the year 3019 as Mordor prepared for the war of the ring, Sauron sent forces to capture Osgiliath once more. This is where the map focuses.
The attackers are led by an ugly orc called the pig, the Orcs are divided into lighter and heavier infantry, coming in several waves. Worse yet, the Captain in charge(called the Wolf) has turned traitor and brings some of his own troops to the battle. He has taken residence in the ruined Dome of the Stars and must be flushed out. For your defence is a sturdy wall that surrounds Osgiliath but the main defence will be a brutal city fight.
Remember, don't fall back an inch without taking that measure of Orcish blood.