In the spring of 1945 the army, now numbering 78,556 soldiers, was redeployed to the front on the Oder river in preparation for the final Soviet offensive of the war in Europe. The Polish Second Army also entered the line of battle at this time, and together the two armies contributed about 10% of the total forces involved in the operation. During the offensive it crossed the river on April 16 and joined the Battle of Berlin. In it, among other actions, Polish units of the 1st Army crossed the Hohenzollern Canal and advanced on Kremmen, Flatow, Paaren and Nauen. They ended their campaign by participating in the Battle of Berlin. In the Berlin Offensive, the First Polish Army's strength was over 74,000, thus making up 7.5% of the strength of the Soviet 1st Belorussian Front, which counted over 980,000 men when the Polish First Army is included in the total. During the Berlin Offensive, the Polish First Army sustained casualties of over 10,400 men. The troops of the 1st Infantry Division supported by the 2nd Howitzer Artillery Brigade and the 1st Independent Mortar Brigade, fought in Berlin around the Technical University and the southwestern side of the Tiergarten close to the Berlin Zoo.