The Mark I British Army heavy tank that entered service in 1916 was agonizingly slow to move, crawling along at a maximum speed of 3.7 mph (6 km/h), so it could easily be outrun and outmaneuvered ...

There were lighter and quicker tanks operating in WWI, like the British-designed Medium Mark A Whippet (pictured), a 14-ton medium tank that used two four-cylinder 45-horsepower engines to achieve ...