Tanks

During WWI mobile warfare on the Western Front had effectively came to a halt.  Both sides were dug in massive defensive positions littered with pillboxes, mine, wire, and strongpoints along rows and rows of trenched defended by thousands of infantry.  Except for gas and artillery attacks the war was at a stalemate.  Any attempt at attack was repelled by a relatively new and awesome weapon, the machine gun.  Tanks were first developed by the British as a sort of mobile pillbox that could advance forward under withering machine gun fire to crush wire and obstacles and to provide fire support for advancing infantry.  

In what many regard as the first truly successful demonstration of the potential of the tank, the entire British Tank Corps (consisting of 474 tanks) saw action at the Battle of Cambrai on 20 November 1917 (although the French can lay claim to its earlier successful use at Malmaison).

In a sweepingly successful start to the battle twelve miles of the German front was breached, with the capture of 10,000 German prisoners, 123 guns and 281 machine guns.

Unfortunately for the British this enormous initial success was effectively cancelled out in German counter-attacks because the British did not possess sufficient infantry troops to exploit the breach they had created.  Many of these early tanks were often lost because of mechanical problems.

On 4 July 1918 the tank was used in a manner that helped to fashion the method in which it was deployed in future battles.  General John Monash, commander of the Australian Corps, launched an attack at Le Hamel by unleashing a coordinated barrage of tanks, artillery and warplanes, all designed to clear a path for advancing infantry.

Monash saw no point in attempting to gain ground by using infantry to storm enemy machine gun positions.  Rather he believed in using technology to facilitate a relatively uneventful infantry advance, with tanks at their head.