Observation planes often operated individually, as did pursuit pilots to attack a balloon or to meet the enemy in a dogfight. However the tendency was toward formation flying, for pursuit as well as for bombardment operations, as a defensive tactic. The dispersal of squadrons among the army ground units (each corps and division had an observation squadron attached) made coordination of air activities difficult, so that squadrons were organized by functions into groups, the first of these being the I Corps Observation Group, organized in April 1918 to patrol the Toul Sector between Flirey and Apremont in support of the U.S. 26th Division. On May 5, 1918, the 1st Pursuit Group was formed, and by the armistice the AEF had 14 heavier-than-air groups (7 observation, 5 pursuit, and 2 bombardment). Of these 14 groups, only the 1st Pursuit and 1st Day Bombardment Groups had their lineage continued into the post-war Air Service. In July 1918 the AEF organized its first wing formation, the 1st Pursuit Wing, made up of the 2d Pursuit, 3rd Pursuit, and 1st Day Bombardment Groups.