Answer based on context:

In June 1916, the British sent out a number of officials to assist the revolt in the Hejaz, most notably Colonel Cyril Wilson, Colonel Pierce C. Joyce, and Lt-Colonel Stewart Francis Newcombe. Herbert Garland was also involved. In addition, a French military mission commanded by Colonel Edouard Brémond was sent out. The French enjoyed an advantage over the British in that they included a number of Muslim officers such as Captain Muhammand Ould Ali Raho, Claude Prost, and Laurent Depui . Captain Rosario Pisani of the French Army, though not a Muslim, also played a notable role in the revolt as an engineering and artillery officer with the Arab Northern Army. The British government in Egypt sent a young officer, Captain T. E. Lawrence, to work with the Hashemite forces in the Hejaz in October 1916. The British historian David Murphy wrote that though Lawrence was just one out of many British and French officers serving in Arabia, historians often write as though it was Lawrence alone who represented the Allied cause in Arabia. David Hogarth credited Gertrude Bell for much of the success of the Arab Revolt. She had travelled extensively in the Middle East since 1888, after graduating from Oxford with a First in Modern History. Bell had met Sheikh Harb of the Howeitat in January 1914 and thus was able to provide a "mass of information" which was crucial to the success of Lawrence's occupation of Aqaba covering the "tribal elements ranging between the Hejaz Railway and the Nefud, particularly about the Howeitat group." It was this information, Hogarth emphasized, which "Lawrence, relying on her reports, made signal use of in the Arab campaigns of 1917 and 1918."

How many years did the Arab campaigns span?
2