For hundreds of years the dagger continued to develop in length, width and quality, and in the 17th Century, it was put to a new use when it was attached to the end of a rifle and became a bayonet. Over time, the dagger became more of a supplementary weapon or specialty weapon, involved in operations where firearms could not be used. During the First World War, the dagger became the weapon of choice for trench warfare, where larger weapons were ineffective. After the war, the dagger was worn with pride as a sign of having served front line duty.
At the beginning of the Second World War, the dagger was part of combat equipment carried by infantry and commando forces. In 1941, after complaints about the quality of the daggers issued, a new dagger called the Fairbairn-Sykes fighting knife, developed by William E. Fairbairn and Eric A. Sykes, was issued to British Commando and other elite units. With first hand knowledge of close-combat gained while serving on the Shanghai Municipal Police Force, Fairbairn and Sykes designed a slender but strong steel dagger. The F-S fighting knife quickly became extremely popular with commandos who used the knife for sentry elimination.