As the war on the Western front became a stalemate, attackers hitting a heavily defended line had to find ways to clear trenches once they reached them and deal with defenders hiding in dugouts. Like many other older siege warfare techniques, such as counter mining and even protective headwear, hand held bombs had been around for a while before they were revived in the trenches of the First World War. Though the British army originally began using handmade grenades, usually the result of engineering soldiers behind the lines with tin cans and some fuse, by 1915 the Mills Bomb had officially entered wartime production.
Mills Bombs were fragmentation grenades, causing flesh shredding damage when they exploded, and viewed by many soldiers as life saving in the close quarter fighting that would occur when clearing a trench. They worked through a pin trigger system, as long as the pin was in the bomb would not explode, at least in theory. The distinctive German stick grenade as also used during the war, and operated using a pull cord running to the detonator; either one was an anti personnel weapon to be feared, and just another sign of the attritional warfare that would mark the conflict.
As infantry battalions in the CEF began to adapt to their war environment, special sections of each were separated and trained specifically in grenade use. After a bombing course, a soldier became a member of the bombing section and would be expected, during battle or during a trench raid, to use the grenades strapped to his midsection, in addition to his other kit, as part of actions to clear a trench. Bombers played a vital role in the smaller bit and hold operations that became synonymous with the latter two years of the war; taking small sections of trench and leapfrogging over one another while clearing them with grenades, proved to be much more successful than simply marching men towards fortified positions.
Bombing sections were also colloquially known as the “suicide squad”, recognizing that they performed a dangerous task in an already terribly dangerous conflict. With whole platoons getting wiped out by a counter attack after taking a trench it is easy to see how volunteering for the bomb section was a very foolhardy move. The grenades developed in the First World War, notably the Mills Bomb and the stick grenade were used well into the Second World War, and indeed current fragmentation grenades can still trace their design back to the original Mills Bomb. Though the First World War did not see the level of house to house fighting as seen in the Second, the principles for dealing with it were born in the trenches on the Western Front.