From July 1942, the US Army Middle East Air Force (USAMEAF, Major-General Lewis H. Brereton) attached USAAF personnel from the 57th Fighter Group and 12th Bombardment Group to DAF fighter and bomber units, as "observers". This was technically a violation of the Arnold-Portal-Towers agreement, which included a stipulation that American personnel should serve only in US units. From mid-September, the P-40 Warhawk squadrons of the 57th FG and the B-25 squadrons of the 12th BG were officially attached to DAF units. On 12 November 1942, USAMEAF was dissolved and replaced by the 9th Air Force, although some US units remained with Commonwealth formations for some time.