Complex sentence: Tenth Air Force was constituted on 4 February 1942 and activated on 12 February, built up around a nucleus of air force personnel newly arrived from Java and the Philippines, under the command of Maj. Gen. Lewis H. Brereton.
Split into simpler sentences: Tenth Air Force was constituted on 4 February 1942 and activated on 12 February. The Tenth Air Force was built up around a nucleus of air force personnel newly arrived from Java and the Philippines, under the command of Maj. Gen. Lewis H. Brereton.