Weapons - Modern Kirpan
In earlier times the sacred kirpan carried by Sikhs had traditionally been the full size tulwar sword. By the 20th century the kirpan carried by Sikhs had evolved from the typical 30 inch blade of a tulwar sword to a short blade less than 18 inches.
Early 20th century kirpan with inlaid mother of pearl handle
12.5 inches in length, ca. 1920's - 1930's, private collection
The change in blade length of the sacred kirpan from a sword to a knife was a difficult one for Sikhs and a direct result of onerous laws passed by the British in India. Under the Indian Arms Act (XI) of 1878, no person could carry arms except under special exemption or by virtue of a licence; the act was applied to the Sikh kirpan. At the advent of World War I, the British government fearing that the ban would affect Sikh recruitment into the British Army, thought it advisable to relax the enforcement of the provision. Between 1914 and 1918, two notifications were issued by the British government giving Sikhs the freedom to possess or carry a kirpan. However the terms of these notifications were vague; the size and shape of the kirpan having remained undefined; prosecution of the Sikhs for wearing, carrying and manufacturing the kirpan continued. During the period of the Gurudwara Reform Movement (1920-1925), the British revoked the notifications and Sikhs were once again prosecuted and imprisoned, Sikh soldiers in the armed forces were even court marshalled and dismissed for keeping kirpans. In 1921 the kirpan factories at Bhera and Sialkot in Punjab were raided and all kirpans exceeding 9 inches in length were seized and the owners of the factories put under arrest. Eventually in 1922 after negotiations between the British and the Shiromani Gurdwara Parbandhak Committee the Sikhs again won the right to carry their kirpans, although now with a much shorter blade. 
Early 20th century Sikh Amrit Ceremony, all the kirpans worn by the initiates are full length swords.
The Sikhs, General Sir John J. H. Gordon, William Blackwood and Sons, Edinburgh and London 1904
1. Harbans Singh, Encyclopaedia of Sikhism, Punjabi University, 1998