SHRAPNEL, SHELL-SHOCK AND SHATTERED DEFENCES

Trench warfare forced military strategists to develop fresh tactics and terrifying new weaponry - in a bid to gain the upper hand

When Private Alex Thompson arrived at Ypres in May 1915, he found himself in the middle of a battle for survival. He was thrust straight into a counterattack against the Germans: the two sides were fighting to secure control of a small hill, known only as "Hill 60".

At 10pm, he left the relative safety of his trench and charged over the top, rifle in hand. Thompson recalled: "We advanced maybe five or 10 yards, [but] some of them never got that length - they were killed going over the trench. That was your training, you see, to just keep going, making for the German trenches."

It was a bloodbath. Thompson recounted:  "It was like pie meat for the Germans, near everyone was getting [trapped] in the barbed wire... They were just cutting us like cutting hay. The fire was rapid, continuous, machinegun fire and shrapnel bursting. You wonder who's going to be shot next and I was shot next."

Although Thompson managed to crawl back into the trench and reach safety, many of his companions weren't so lucky. For the next two years, the Allies failed to gain control of that one, small hill.

Millions of men perished in trench warfare, but it was one of the defining strategies of World War I - particularly on the Western Front. However, this strategy was nothing new: armies had been holing down in the earth for centuries, to avoid having soldiers exposed.

But World War I saw the strategy explode. There were several reasons for this: before the war had broken out, military technology had vastly improved: the machine gun had been unveiled in 1884, and artillery had been consistently upgraded since the late 19th century. As well as facing deadly weapons, in 1914 more soldiers were on the battlefield than ever before - meaning more men needed protection.