1918 proved to be the costliest year of the war for the Allies.
At the advent of the war, Russia invaded Germany and Austria as retaliation for its ally Serbia being invaded.
The war at sea was one of blockades and sinkings, led by the feared U-boats.
The new development of aerial combat - from bomb squadrons to sea planes.
Focusing on life in the trenches during WWI with color-doctored footage.
In four years of war, 65 million men took up arms, with ten million killed and another 20 million incapacitated.