US military forces fire a howitzer during a joint military training exercise with the Philippines in Tarlac province, north of Manila, in 2016. Reuters
Second World War 155mm howitzers fire shells at enemy lines from advanced positions in Guadalcanal, Solomon Islands, where US Marines led the attack on Japanese forces, in January 1943. Getty Images
Troops of a field artillery battery emplace a howitzer in France, following the advance of the infantry and are setting up a new position. in 1944. Getty Images
A CH-54 'Flying Crane' helicopter brings in a 155mm howitzer, circa 1968. Getty Images
US artillery crews in South Vietnam load shells in howitzers, in 1971. Getty Images
US Marines clean and service a 155mm howitzer at their position as a peacekeeping force inside Beirut International Airport, in 1984. Getty Images
Marines hold their ears upon the firing of an artillery round from a 155mm howitzer at a target in southern Iraq, in 2003. Getty Images
Soldiers load fuses on to high explosive rounds to use in a howitzer at FOB Joyce in Afghanistan's Kunar province, in 2012. Reuters
Howitzers unloaded at Beirut port after a shipment from the US military aid to the Lebanese army, in 2015. EPA
US military forces fire a howitzer during a joint military training exercise with the Philippines in Tarlac province, north of Manila, in 2016. Reuters
Second World War 155mm howitzers fire shells at enemy lines from advanced positions in Guadalcanal, Solomon Islands, where US Marines led the attack on Japanese forces, in January 1943. Getty Images
Troops of a field artillery battery emplace a howitzer in France, following the advance of the infantry and are setting up a new position. in 1944. Getty Images
A CH-54 'Flying Crane' helicopter brings in a 155mm howitzer, circa 1968. Getty Images
US artillery crews in South Vietnam load shells in howitzers, in 1971. Getty Images
US Marines clean and service a 155mm howitzer at their position as a peacekeeping force inside Beirut International Airport, in 1984. Getty Images
Marines hold their ears upon the firing of an artillery round from a 155mm howitzer at a target in southern Iraq, in 2003. Getty Images
Soldiers load fuses on to high explosive rounds to use in a howitzer at FOB Joyce in Afghanistan's Kunar province, in 2012. Reuters
Howitzers unloaded at Beirut port after a shipment from the US military aid to the Lebanese army, in 2015. EPA
US military forces fire a howitzer during a joint military training exercise with the Philippines in Tarlac province, north of Manila, in 2016. Reuters