The RFC was also responsible for the manning and operation of observation balloons on the Western front. When the British Expeditionary Force (BEF) arrived in France in August 1914, it had no observation balloons and it was not until April 1915 that the first balloon company was on strength, albeit on loan from the French Aérostiers. The first British unit arrived 8 May 1915, and commenced operations during the Battle of Aubers Ridge. Operations from balloons thereafter continued throughout the war. Highly hazardous in operation, a balloon could only be expected to last a fortnight before damage or destruction. Results were also highly dependent on the expertise of the observer and was subject to the weather conditions.