Schlieffen Plan, which was the German Army's strategic plan for a quick end to the War by invading France through Belgium.

Despite initial territorial gains, the Germans were unable to achieve their goals, not least because of fierce resistance from the French, who proved much more resilient than the Germans had expected.

But at the same time, the French and their British allies were unable to make much of a breakthrough from their numerous counter-attacks, and so it wasn't very long into the War before both sides hunkered down for the long-haul, digging huge trenches across vast swathes of the Northern French and Belgian countryside.

In the Eastern Front, meanwhile, the Germans and their Austro-Hungarian allies were generally much more successful in reaching their strategic goals, so fighting tended to be much more mobile, with greater movement both in men and artillery.

As a consequence, tactical offensives were much more common in this theatre of war than in the West, where the stalemate of the trenches encouraged a more defensive mindset, both tactically and strategically. To be sure, sporadic offensives did take place on the Western Front from time to time, but they had little effect overall, making no more than minor territorial gains at the cost of an appalling loss of life.