Dmitrii Pavlovich Grigorovich was most important designer/constructor of pre-revolutionary Russia who continued work in Soviet Union. First 23 designs were in Russia, almost all being single-engined pusher biplane flying-boats starting 1912 with M-1 based on Donnet-Lévêque. Estimated 500 built of M-9 alone. After 5 years of civil war Grigorovich resumed work at GAZ-3 with upgraded flying-boats, but from 1924 added fighters (from I-1, I-2bis), civil transports (e.g. SUVP) and from 1927 large multi-engined monoplane flying-boats. TB-5 heavy bomber of 1931 was largest aircraft produced by first group of VT (internal prison) detainees, of whom Grigorovich was oldest and most senior. Most later designs were fighter and attack aircraft, ending with DG-58 (PB-1) dive-bomber of 1936.