Friendly fire
The offensive on Bologna started on 9 April at 4:00 am local time, with a major air and artillery bombardment of 400 guns firing on German positions, followed by an advance of ground forces the same evening. Friendly fire caused casualties as American bombers killed 38 advancing Polish troops on that day. The American and British units engaged the German flanks, while the Polish units broke through to the city. On 10 April, Polish forces pushed the Germans away from the Senio River. From 12–14 April Polish forces fought the Germans at the Santerno River and captured Imola. From 15–16 April, the Poles fought at the Sillaro River and the Medicina Canal. On 17 April, the commander of the Eighth Army ordered the Polish forces to continue their push towards Bologna from the east. The town was to be taken initially by the American troops of the Fifth Army advancing from the south.