During 1916, aerial reconnaissance patrols had most often been unaccompanied as there had been little if any aerial disputes, between the belligerents. However, just as the Sinai and Palestine Campaign ground war on the Gaza to Beersheba line came to resemble trench warfare on the western front, so too did the air war over southern Palestine come to resemble that being fought over France. After the Second Battle of Gaza in April 1917 and during the Stalemate in Southern Palestine which followed, the concentration of Egyptian Expeditionary Force (EEF) and Ottoman Army forces holding established front lines grew, as associated supply dumps and lines of communications were developed. The need to know about these fuelled "intense rivalry in the air". Aerial reconnaissance patrols were regularly attacked, so it was necessary for all photography and artillery observation patrols to be accompanied by escort aircraft. These special EEF patrols which grew into squadrons, accompanied and protected the reconnaissance aircraft, attacking hostile aircraft wherever they were found, either in the air, or on the ground. However the technically superior German aircraft shot down numbers of EEF aircraft during dog fights.