Trench warfare
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–1918, both sides constructed elaborate trench, underground, and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, camouflaged trapping pits, and other obstacles. The area between opposing trench lines (known as "no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties.
United Kingdom of Great Britain and Ireland
Britain entered the war to protect Belgium from German aggression, and quickly assumed the role of fighting the Germans on the Western Front, and dismantling the overseas German Empire. The romantic notions of warfare that everyone had expected faded as the fighting in France bogged down into trench warfare. Along the Western Front the British and French launched repeated assaults on the German trench lines in 1915–17, which killed and wounded hundreds of thousands, but made only limited gains. By early 1916, with number of volunteers falling off, the government imposed conscription in Britain (but was not able to do so in Ireland where nationalists of all stripes militantly opposed it) in order to keep up the strength of the army. Industry turned out munitions in large quantities, with many women taking factory jobs. The Asquith government proved ineffective but when David Lloyd George replaced him in December 1916 Britain gained a powerful and successful wartime leader.