Complex sentence: The company was established in 1946 in Novosibirsk as a top-secret Soviet Research and Design Bureau No.153, headed by Oleg Antonov and specialised in turboprop military transport aircraft.
Split into simpler sentences: The company was established in 1946 in Novosibirsk as the top-secret Soviet Research and Design Bureau No.153. It was headed by Oleg Antonov and specialised in turboprop military transport aircraft.