<P> Because attacking an entrenched enemy was so difficult, tunnel warfare became a major effort during the war . Once enemy positions were undermined, huge amounts of explosives would be planted and detonated as part preparation for an overland charge . Sensitive listening devices that could detect the sounds of digging were a crucial method of defense against these underground incursions . The British proved especially adept at these tactics, thanks to the skill of their tunnel - digging "sappers" and the sophistication of their listening devices . </P> <P> At the beginning of the war, artillery was often sited in the front line to fire over open sights at enemy infantry . During the war, the following improvements were made: </P> <Ul> <Li> The first "box barrage" in history was fired at Neuve Chapelle in 1915; this was the use of a three - or four - sided curtain of shell - fire to prevent the movement of enemy infantry </Li> <Li> The wire - cutting No. 106 fuze was developed, specifically designed to explode on contact with barbed wire, or the ground before the shell buried itself in mud, and equally effective as an anti-personnel weapon </Li> <Li> The first anti-aircraft guns were devised out of necessity </Li> <Li> Indirect counter-battery fire was developed for the first time </Li> <Li> Artillery sound ranging and flash spotting, for the location and eventual destruction of enemy batteries </Li> <Li> The creeping barrage was perfected </Li> <Li> Factors such as weather, air temperature, and barrel wear could for the first time be accurately measured and taken into account when firing indirectly </Li> <Li> Forward observers were used to direct artillery positioned out of direct line of sight from the targets, and sophisticated communications and fire plans were developed </Li> </Ul> <Li> The first "box barrage" in history was fired at Neuve Chapelle in 1915; this was the use of a three - or four - sided curtain of shell - fire to prevent the movement of enemy infantry </Li>

What resulted from the combination of rifles and trenches