In August 1918, the Allies intended to launch two offensives, one led by British commander Douglas Haig near Amiens, and the other by American John J. Pershing near Saint-Mihiel. Prior to the Battle of Amiens, Haig's subordinate Henry Rawlinson, commander of the British Fourth Army, employed several deceptive tactics, including periods of radio silence by units involved in the coming attack and false radio traffic from other parts of the British lines. In addition, Rawlinson delayed troop movement for as long as possible prior to the start of the attack to prevent German observers from obtaining data on his disposition of forces, and moved troops and materiel almost entirely at night. The British offensive was immediately successful because they had maintained the element of surprise. British troops and tanks advanced eight miles, captured 400 artillery pieces, and inflicted 27,000 casualties, including 12,000 prisoners.