Complex sentence: During the initial stages of World War I, shrapnel was widely used by all sides as an anti-personnel weapon, usually defensively, and was in fact the only type of shell available for British field guns (13-pounder and 18-pounder).
Split into simpler sentences: During the initial stages of World War I, shrapnel was widely used by all sides as an anti-personnel weapon. It was the only type of shell available for British field guns (13-pounder and 18-pounder).