By December 1914 the Germans' had been halted at the Marne. The opposing armies sat astride a line from the Swiss frontier to the Belgian coast for four years. An outflanking manoeuvre was impossible, the only route was through the enemy lines. The Allies mounted a series of offensives with increasing intensity, growing casualties and little gain. At Passchendaele in 1917 4¼ million shells were fired at the enemy but in 14 weeks the allies lost half a million men and gained just 4 ½ miles. Something else was needed. The navy contributed to the early development of the tank. In 1914 the Navy sent a detachment of Marines to Belgium to harry the enemy during the allied retreat. Commander Charles Samson and his team used his brother's Mercedes armed with a machine gun to patrol inland and harry the enemy. Churchill saw the potential. An armoured car on a Rolls-Royce chassis was developed. Meanwhile, Colonel Ernest Swinton was in France as a correspondent. He concluded that an armed caterpillar tractor might be able to cross the shell-torn ground. After many setbacks he persisted and a new design eventually became 'Little Willie' - the first 'tank'. The need for secrecy led to a name for the new weapon. It was suggested it looked like an oil tank and the name stuck. Tanks were first used in the Battle of the Somme in 1916 and in 1917 the Hindenburg Line was breached. The tanks had shown the way and the Battle of Cambrai set the pattern for a new form of attack which led to the opening of the front and the end of the war.