塹壕
The war now became a stalemate – the famous "Western Front" was fought largely in France and was characterized by very little movement despite extremely large and violent battles, often with new and more destructive military technology. On the Western Front, the small improvised trenches of the first few months rapidly grew deeper and more complex, gradually becoming vast areas of interlocking defensive works. The land war quickly became dominated by the muddy, bloody stalemate of Trench warfare, a form of war in which both opposing armies had static lines of defense. The war of movement quickly turned into a war of position. Neither side advanced much, but both sides suffered hundreds of thousands of casualties. German and Allied armies produced essentially a matched pair of trench lines from the Swiss border in the south to the North Sea coast of Belgium. Meanwhile, large swaths of northeastern France came under the brutal control of German occupiers.