On 15 March, the Whites launched their major offensive against the Reds in the northern Häme where the Red front collapsed in a couple of days. The Whites were now able to besiege Tampere, militarily the most important Red town. The Battle of Tampere was fought from 23 March to 6 April. It was the fiercest battle of the Finnish Civil War, and at the time, also the largest urban battle in the world. The Battle of Tampere ended with mass executions of surrendering Reds, of whom 10,000–11,000 were captured, and thousands fled the surrounding areas.