<P> For a time, in 1914--1915, some hoped that the war could be won through an attrition of materiel--that the enemy's supply of artillery shells could be exhausted in futile exchanges . But production was ramped up on both sides and hopes proved futile . In Britain the Shell Crisis of 1915 brought down the British government, and led to the building of HM Factory, Gretna, a huge munitions factory on the English - Scottish border . </P> <P> The war of attrition then focused on another resource: human lives . In the Battle of Verdun in particular, German Chief of Staff Erich Von Falkenhayn hoped to "bleed France white" through repeated attacks on this French city . </P> <P> In the end, the war ended through a combination of attrition (of men and material), advances on the battlefield, arrival of American troops in large numbers, and a breakdown of morale and productivity on the German home - front due to an effective naval blockade of her seaports . </P> <P> As with most other technologies, the aircraft underwent many improvements during World War I . </P>

Which of the following was not a technology used during world war 1