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.

Military dogs in World War One were positioned in a variety of roles, depending on their size, intelligence and training. Generally, the roles fell into the category of sentry dogs, scout dogs, casualty dogs, explosive dogs, ratters and mascot dogs.

Sentry dogs These dogs were patrolled using a short leash and a firm hand. They were trained to accompany usually one specific guard and were taught to give a warning signal such as a growl, bark or snarl to indicate when an unknown or suspect presence was in the secure area such as a camp or military base. Dobermans have traditionally been used as sentry dogs and are still widely used today as guard dogs.

Scout dogs These dogs were highly trained and had to be of a quiet, disciplined nature. Their role was to work with soldiers on foot patrolling the terrain ahead of them. These dogs were useful to the military because they could detect enemy scent up to 1000 yards away, sooner than any man could. Instead of barking and thus drawing attention to the squad, the dogs would stiffen raise its shackles and point its tail, which indicated that the enemy was encroaching upon the terrain. Scout dogs were widely used because they were highly efficient in avoiding detection of the squad.