No. 15 ball grenade

The No. 15 ball grenade was a grenade used by the British during World War I.

Overview
The No 15 is a time-fused grenade. It is internally fragmented and uses a cast-iron body.

To light the grenade, the user has to remove a covering that was on the fuse, then strike an external Brock matchhead igniter against the fuse.

There are two types of fuses; the five-second and the nine-second. The former was intended for throwing, while the latter was intended for catapults.

History
The No 15 was one of the interim grenades created because of the problems associated with the No 1 grenade. Unlike the others, the No 15 had been created specifically for the Middle Eastern theatre of World War I, mostly for the fighting in the Dardanelles.

While crude, the No 15 did well in the Dardanelles. In addition, it could easily be mass-produced; in September 1915, more than 200,000 No 15s were created per week.

However, there were a few problems; the explosive charge was too large, which created smaller-than-expected fragmentation when the grenade exploded. In addition, it was considered too large because of its 3 in circumference. These problems were fixed with the No 16 oval grenade.

Battle of Loos
The No 15 was to be a key part in the Battle of Loos. Tacticians envisioned that the No 15 would be a great help in breaching German defenses. The No 15 was used because the No 5 "Mills bomb" was not being delivered properly to forces in the Western Front, and not enough of them could be supplied before the start of the Loos campaign.

When the Battle for Loos started, the No 15 failed to work. The fuse had become so wet that it was impossible to start it. In fact, it was estimated that approximately 18 out of 20 No 15s failed to light up in the first place. Its failure nearly led to the British being defeated at Loos.

On November 20, 1915, the No 15 and its cousin, the No 16, were withdrawn from France and were replaced with the No 5 "Mills bomb".

No 16 "oval grenade"
The No 16 is essentially an improved version of the No 15. Instead of a ball shape, it has an oval shape and has less explosive charge. It was planned to completely replace the No 15, but the defeat at Loos caused both the No 15 and No 16 to be withdrawn from service, as they both had the same lighting system.