To begin with, World War One was a war of movement – there were even cavalry charges with men on horseback using swords to attack the enemy.
By the late summer of 1914, the German army had fought its way to within sight of the Eiffel Tower but failed to capture Paris or force the French to surrender.
Once halted, the Germans started digging trenches for their soldiers to shelter from enemy fire, the French and British did the same.
Fairly soon, a network of trenches stretched for 400 miles from the Channel coast to the border with Switzerland. This was called the Western Front. The war of movement was at an end. For most of the next four years neither side managed a decisive breakthrough and the Western Front became deadlocked in trench warfare.
Trenches were usually about seven feet deep and six feet wide. Duck-boards were placed at the bottom to protect soldiers from problems such as trench foot.
Soldiers made dugouts in the sides of the trenches to give them some protection from the weather and enemy fire. The front-line trenches were also protected by barbed wire and machine-gun posts.
Behind the front-line trench there were support and reserve trenches. The three rows of trenches covered between 200 and 500 yards of ground. Communication trenches were dug at an angle to the front-line trench and were used to transport men, equipment and food supplies.
Men usually only spent a few days at the front line before being sent back to reserve trenches, then back to rest and recovery positions.
However, soldiers often spent much longer at the front. For instance, the Black Watch, a famous Scottish regiment, once served for 48 days without a break. Soldiers had to endure harsh conditions:
The stalemate on the Western Front meant that both sides tried to break through the enemy's defensive positions, meaning troops would be sent over the top in frontal assaults, resulting in high numbers of casualties.