To have air support on Sumatra and to replace the RAF Spitfire unit stationed on Medan, 122 Squadron was established November 1 1946 on 1VB Tjililitan in Jakarta.

After 1942 ML-KNIL continued to fly in Australia and New Guinea with the Curtiss P-40, but by 1945 this type was obsolete. Therefore the American authorities were asked for re-equipment with 41 aircraft of the type P-51 Mustang, beginning with 120 squadron^[1].
The Mustangs were prepared at RAAF depots in Australia at the Dutch 'Personnel and Equipment Pool' (NEI-PEP)^[2] in Brisbane.

On May 1 1946 121 Squadron^[3] was established at Tjililitan airfield. This was commanded by Major Hans Maurenbrecher, the ex-commander of 120 Sqn. The first personnel of this new squadron also consisted of war veterans of 120 Sqn. The first months were spent on pilot retraining and operational training.

Personnel and aircraft where transfered from 121 to 122 Squadron. The 121 Squadron at Tjililitan took care of the transfer of personnel and equipment to Medan in October 1946 and it also relinquished part of its ground personnel and pilots ^[2].

Under the command of Captain Gerard Deibel, 12 P-51s of the 122 Sqn and the technical staff in a B-25, flew on November 14 1946 from Tjililitan to their Polonia base at Medan, a distance of 1390 km. Reinforcement with 5 aircraft arrived on November 19.

In the B-25, a team from the technical service was under the command of adjudant C.W. Bastiaans ^[4].