howitzers, a barrel shorter trajectory is bent, suitable for field artillery in the fight against concealed targets and ground targets. As early as the 17th century, the European angle larger artillery fired bombs as howitzers. The mid-19th century, howitzers variable charge angle of 12 ° -30 °, gun length is 7-10 times the caliber. In the First World War, the Xu army competing equipment howitzer, the new models continue to emerge. At that time, the howitzer cannon length 15-22 times the caliber, the maximum range of up to 14,200 meters, the maximum angle is 45 °.