Jacob remained in London until May 1941 when became a war correspondent for the "Daily Express". He sailed to Cairo, taking the long sea route via Cape Town. He spent the next two years with the 8th Army in North Africa, initially covering the Siege of Tobruk and Operation Crusader. He was withdrawn from Tobruk shortly before it fell to the Germans and was posted to Tehran where he received permission from the Soviet Embassy to visit the Red Army in Azerbaijan. He returned to Egypt for the first and second Battle of El Alamein, before traveling to India. He covered Wingate's first 'Chindit' expedition in Burma, and the circumstances of Gandhi's fast. In the Soviet Union for four months, he covered the Battle of Kursk and Stalin's counterattack. He described his experiences in "A Traveler's War" published in 1944.