made by the Indian Corps in France by December 1914. It was a smooth tube firing a 4 pound "tin-pot" filled with ammonal. The fuze was a length of Bickford fuse ignited by the burning of the propellant, which made it too dangerous for long term use. By the end of June 1915, another 100 had been manufactured and sent to France and 20 to Gallipoli. Vickers 1.57-inch mortar The Vickers 1.57-inch trench mortar was first introduced to France in March 1915, 127 by the end of June, and about 275 were manufactured until it was withdrawn in January 1917, after being replaced by the 2-inch mortar. The 1.57-inch was similar to the eventual 2-inch model, but the particular Vickers design was complicated and expensive to manufacture. It fired either an 18 or 33 pound cast-iron bomb filled with Permite (perchlorate), but the smaller bomb was considered too light and the heavier had a range of only 200 yards. The 2-inch medium mortar This was designed and manufactured by the Royal Ordnance Factories in early 1915 and introduced along with the 1.57-inch mortar in March 1915. It incorporated what was known of the German prewar Krupp mortar. This was the first design to meet all the requirements, after modifications to simplify manufacture; it fired a good-sized spherical cast-iron bomb of 42 pounds (total projectile weight 51 pounds with stick and fuze), considered the largest practical size for use from trenches, at ranges from 100 to 600 yards using a simple 2-inch tube as the mortar body. The mortar and ammunition could be cheaply manufactured by small unsophisticated "trade" workshops; the bomb was safely detonated by a standard No. 80 "time and percussion" artillery fuze. Drawbacks were that the steel tail was usually projected backwards towards the firer when the bomb detonated, resulting in occasional casualties and the No. 80 fuze was also required by the 18-pounder field guns which were given priority, limiting mortar ammunition supply to the front until early 1916 when a special cheap trench mortar fuze was developed. The 2-inch mortar served in limited numbers in France in 1915 from March, with early mortars and ammunition made by the Royal Ordnance Factory, with the Vickers 1.57-inch model. Mass production began with an order in August 1915 for 800 mortars from several railway workshops and agricultural machinery makers, together with an order for 675,000 bombs from numerous small