They were not accustomed to the continental weather and were poorly equipped to resist the cold, leading to low morale which was further compounded by the reserve system, whereby reinforcements were drafted in from any regiment and had no affiliation to their new units. Officer casualties were even more of a handicap, as replacements were unfamiliar with the Indian Army and could not speak the language. With morale low, many soldiers fled the scene of the battle and the infantry divisions were finally withdrawn to Mesopotamia in October 1915, when they were replaced by the new British divisions of Kitchener's Army. With the withdrawal of the infantry divisions, the only Indian Army units on the Western Front were the two cavalry divisions. In November 1916, the two Indian cavalry divisions were renumbered from 1st and 2nd to the 4th and 5th Cavalry Divisions. Serving alongside British cavalry divisions they were held behind the front line awaiting the hoped for breakthrough. At times during the war they served in the trenches as infantry, each cavalry brigade when dismounted formed a dismounted regiment. This meant that when the divisions went into the front line, they could only cover a brigade area. Before being themselves withdrawn to Egypt in March 1918, they took part in the Battle of the Somme, the Battle of Bazentin, the Battle of Flers-Courcelette, the advance to the Hindenburg Line and finally the Battle of Cambrai. Of the 130,000 Indians who served in France and Belgium, almost 9,000 died. In 1914, the Governor of British East Africa requested assistance to deal with the German forces in German East Africa and the problem was handed to the India Office, which assembled two forces and shipped them to his aid. Indian Expeditionary Force B consisted of the 27th (Bangalore) Brigade from the 9th (Secunderabad) Division and an Imperial Service Infantry Brigade, a pioneer battalion, a mountain artillery battery and engineers were sent to Tanganyika with the task of invading German East Africa. The force under the command of Major General Arthur Aitken landed at Tanga on 2–3 November 1914. In the following Battle of Tanga, Aitkens' 9,000 men were badly beaten by the 1,000 men under their German commander Paul von Lettow-Vorbeck. The force re-embarked on 5 November 1914, having suffered 4,240 casualties and the loss of several hundred rifles, 16 machine guns and 600,000 rounds of ammunition. Indian Expeditionary Force C was the second force assembled for service in British East Africa in 1914.