Apart from naval and aerial needs, a reminiscent picture of the Western Front during the three or four years of trench warfare reveals the predominant importance of petroleum. It proved a decisive factor as early as the Battle of the Marne. It will be recalled that one of the greatest factors in Marshal Joffre’s victory was the feat of General Gallieni in transporting a fresh army from the Paris area to the front by commandeering nearly every motor car and taxicab in Paris. Thus, petrol transport hastily improvised saved Paris and turned the scale of the 1914 campaign against the Germans. It will be recalled that the conflict then settled down to a prolonged era of trench warfare. The Allies commenced the construction of strategic railways to support the armies of the line, but between the railheads and the actual battlefront in the long stretch from the North Sea to the borders of Switzerland, transport was almost wholly dependent on motor spirit or gasoline. Innumerable heavy motor lorries carried food, guns and ammunition to the fighting forces. But the function of petroleum products on land did not end in its association with commissariat and supply. It was an aggressive instrument. The greatest new factor in land fighting that the war developed was the “tank”--a land battle cruiser, first introduced by the British at the Battle of the Somme in July, 1916, and afterwards adopted by all armies. This great instrument of war was wholly dependent on petroleum products for its power of movement. Without the internal combustion engine operated by gasoline it would have been an immobile toy. Again, when liquid fire came into use petroleum was the basis; and in another great destructive agent--the explosive, known as T. N. T.--toluol, which is found in some of the heavier grades of petroleum, was a basic constituent. Though petroleum in the hands of inventors became an agent of terrible destruction, it had its beneficent uses in battle as well as in periods of tranquility. Armies organized on so vast a scale could not have been fed without it. When the battle raged the Red Cross vehicles which performed the work of transporting the wounded to the dressing stations and field hospitals were propelled by gasoline. And when darkness had fallen on the fray the oil lamp and the paraffine candle were lighted to cheer the tired soldiers. An English writer who visited the front in 1917 wrote of the all-pervading uses of petroleum: “It was to be found wherever there was a vestige of life in those zones of battle; the soldiers in their, at times, lonely dug-outs, used oil for cooking as well as light, and all traffic was guided from disaster along the roads by the use of oil, which also offered the only source of artificial light in the Red Cross vehicles. What an immense organization it was which depended for its ceaseless activities upon the products of petroleum.”