Caterpillar D6

The Caterpillar D6 track-type tractor is a medium bulldozer manufactured by Caterpillar Inc. with a nominal operating weight of 18 tons. The military versions were classified as the SNL G152 medium tractor, under the G-numbers classification system used for army tractors.
D6 Version history.
The D6 started out in 1935 as the RD6, fitted with a 3-cylinder 45 hp D6600 engine. The numbering was changed to the D6 in 1937.
Caterpillar first introduced the entirely new D6 in 1941 with the 4R & 5R series. This was powered by the D4600 engine of 55 hp (drawbar).
Dozer blades.
The dozer blade on front of the tractor can come in different varieties: 
Rear equipment.
The rear of the machine can be outfitted with various work tools to complement the front blade:
The crawler tractor is powerful, yet small and light weighing 16 to 20 tons (18 to 23 short tons) depending on configuration. This makes it ideal for working on very steep slopes, in forests, and for backfilling pipelines safely without risking damage to the pipe.
A low ground pressure version is also available with extra wide tracks to provide low ground pressure which allows working in muddy areas without sinking.