On 16 April the Russians and Poles attacked the Seelow Heights . Almost 1,000,000 Russians\/Poles with 20,000 artillery pieces were fighting against 100,000 Germans with 1,200 tanks . The Battle of the Seelow Heights , fought over four days from 16 April until 19 April , was one of the last pitched battles of World War II : almost one million Red Army troops and more than 20,000 tanks and artillery pieces were deployed to break through the `` Gates to Berlin '' which were defended by about 100,000 German soldiers and 1,200 tanks and guns .