The dog has been at man's side since the wolf first moved into the cave. We can't know where, when and how this was accomplished, but the why is very clear: it benefits both parties. Even when man has gone to war, the dog has gone with him.
The Greek battle dog as a recognizable type of dog was established in the Epirus region in what has become northwestern Greece -- the birthplace of Olympias, wife of Philip II of Macedon and mother of Alexander the Great. The Romans named this dog "canis molossus." It was a multipurpose dog of medium size and stout build, used primarily to guard the farms, flocks and herds. An interesting amphora or vase of the Late Archaic period shows a Greek warrior or hoplite leaving home, as a dog stands between him and a woman who may be his wife; the dog is seen from the rear and is looking up at the woman. Perhaps he's the dog who followed his master to war against the Persians, as depicted in Polygnotos' mural of the Battle of Marathon, painted in the Stoa Poikile -- the Painted Porch -- a large public building forming part of one side of the agora, or marketplace, of ancient Athens.
Gods and Dogs
The Greeks included dogs in their pantheon of deities in the same kind of roles that dogs filled in the human world. Cerberus, the three-headed dog, guarded the gates of the underworld, just as a Molossian guarded the farmstead. The dog was the sacred animal of Ares, god of war, and the goddess Artemis kept hunting dogs, but Hekate, goddess of witches, ghosts and transitions, kept black Molossian bitches as her familiars. Folk wisdom says only dogs can see this grim goddess on her nighttime travels.
From One Root, Many Branches
Many modern breeds claim descent from the Molossian type, including the boxer, the pit bull and various mastiffs. Dog DNA is notoriously plastic, and many different-appearing dogs can be obtained by selective breeding in a relatively short period of time, so this is far from impossible. However, the basic personality traits that make a dog a dog are less readily altered. The tiniest Chihuahua can be as fierce as a Greek battle dog advancing on the enemy.
Modern Warrior Dogs
Greek battle dogs charged into the fray protected by knife-studded leather collars for both offense and defense, while modern U.S. war dogs are armored in Kevlar. Modern battle dogs are not such dedicated fighters as their Greek ancestors, as they are used to detect both explosive devices and intruders and to locate people in hiding, as well as to bring down and control fugitives, but they are also trained to attack on their own initiative anyone who attacks their handlers. At least one dog accompanied the SEAL raid to capture Osama bin Laden, and another may have been the warrior who found Saddam Hussein in his spider hole.