The envelopment is a maneuver in which a secondary attack attempts to hold the enemy 's center while one single envelopment or both flank (Goodman, R.E.M., 1993). Double envelopment is where the enemy is attacked or overlapped in a push to the enemy 's rear in order to threaten the enemy 's communications and line of retreat. This forces the enemy to fight in several directions and possibly be destroyed in position. New variations include vertical envelopments or Airborne Troops or airmobile troops and amphibious envelopments (Goodman, R.E.M., 1993). Noted single envelopments were accomplished by Alexander the Great at Arbela in 331 BC, Robert E. Lee at Chancellorsville in 1863, and Erwin Romme at Gazala in 1942, leading to the capture of Tobruk (Goodman, R.E.M., 1993). Famous double envelopments include those of Hannibal at the Battle of Cannae in 216 BC, the American Revolutionary War Battle of Cowpens in 1781, and the destruction of the 7th German Army at the Falaise Gap in 1944 (Goodman, R.E.M., 1993). Defensive-offensive maneuvers include attack from a strong defensive position after the attacking enemy has been sapped in strength, as in two battles of the Hundred Years ' War, Crecy in 1346 and Agincourt in 1415, or feigned withdrawals that attempts to lure the enemy out of position as performed by William the Conqueror at the Battle of Hastings in 1066 and also by Napoleon at the Battle of Austerlitz in 1805 (Goodman, R.E.M., 1993),(Greene, 2006). Turning maneuvers