In 1958 Bonatti joined an Italian expedition, led by Riccardo Cassin, to the Karakoram mountains of Pakistan. The intention was to climb the previously unconquered Gasherbrum IV (, the 17th highest mountain on Earth and the 6th highest in Pakistan). On 6 August together with Carlo Mauri, Bonatti summitted after an alpine style ascent by the north-east ridge. The route climbed by Bonatti and Mauri has since been successfully climbed only a few times.