The Scammell Pioneer was a British 6×4 tractor unit used in World War II as an artillery tractor, recovery vehicle and tank transporter.
A British Army Scammell Pioneer towing an 8-inch howitzer of 1st Heavy Regiment, near Calais (12 January 1940)
The prototype tank transporter of 1929, H 22509, loading a Medium Mark II
Pioneer artillery tractors in the London Victory Parade, June 1946
Pioneer recovering a Universal Carrier, Sussex 1941
A 6×4 or six-by-four is a vehicle with three axles, with a drivetrain delivering power to wheels at the ends of two of them. It is a form of four-wheel drive but not one of all-wheel drive.
Typical American 6×4 tractor unit
1937 military lorry off-road
TACR2 airfield fire engine