In 1944, Hackett raised and commanded the 4th Parachute Brigade for the Allied assault on Arnhem, in Operation Market Garden. In battle at Arnhem Brigadier Hackett was severely wounded in the stomach, was captured and was taken to the St. Elizabeth Hospital in Arnhem. A German doctor at the hospital wanted to administer a lethal injection to Hackett because he thought that the case was hopeless. However, he was operated on by Alexander Lipmann-Kessel, who, with superb surgery, managed to save the brigadier's life.