The 152 mm howitzer M1954, also known as the D-20 is a manually loaded, towed 152 mm artillery piece, manufactured in the Soviet during the 1950s. It was first observed by the west in 1955 and was therefore known as the M1955. There is also a Chinese copy, called Type 66.
The barrel length of the gun is 25 calibers. The D-20 was the first 152-mm cannon system to incorporate a semiautomatic vertical-sliding-wedge breech block
The gun was also used for the self-propelled 2S3 Akatsiya.
The D-20 is in operation in at least 13 countries and has been license manufactured in the People's Republic of China as the Type 66 (or the improved version Type 66-1). Its self-propelled version known as Type 83 was first introduced in the mid-1980s.
Yugoslavia also produced a further developed gun called the M84 NORA-A.