Dogs had a vital part to play in World War One as the complexes of trenches spread throughout the Western Front. It is estimated that by 1918, Germany had employed 30,000 dogs, Britain, France and Belgian over 20,000 and Italy 3000. America, at first, did not use dogs except to utilise a few hundred from the Allies for specific missions. Later, after a chance stowaway, the USA produced the most decorated and highly-ranked service dog in military history, Sergeant Stubby.

Lots of dog breeds were used during World War One, but the most popular type of dogs were medium-sized, intelligent and trainable breeds. Two in particular were used because of their superior strength, agility, territorial nature and trainability; Doberman Pinscher's and GSDs, both native to Germany. Doberman's were used because they are both highly intelligent and easily trainable, and possess excellent guarding abilities. Being of slight frame and extremely agile, their dark coat allowed them to slip undetected through terrain without alerting the enemy. They were employed most frequently in Germany. German Shepherd's were used also because of their strength, intelligence and trainability, being eager to please their masters. Other breeds associated with WWI were smaller breeds such as terriers, who were most often employed as 'ratters'; dogs trained to hunt and kill rats in the trenches