Foreign Policy has an excellent photo essay on America's active duty canines. The Army alone has 2800. SEAL Team 6 had a dog with them on the Bin Laden raid.
"When you're going on a mission," Dowling says, "a raid or a patrol, insurgents are sneaky -- they like to hide stuff from you. But a dog can smell them. .... [Think about] Saddam Hussein ... what if Osama had been [hiding] in a hole in the ground? A dog could find that. A dog could alert them to where he's hiding because of the incredible scent capabilities. ... You can only see what you can see. You can't see what you don't see. A dog can see it through his nose."
When not sniffing out explosives or hiding insurgents, these dogs serve a secondary role. There is no better therapy to come down from an adrenalin rush after a nerve-wracking, heart-pounding mission, than to be greeted by a devoted dog.
And these dogs are very devoted.
When Private First Class Colton Rusk was shot after his unit came under Taliban sniper fire during a routine patrol in Afghanistan, Rusk's bomb-sniffing dog, Eli, crawled on top of his body, attacking anyone -- including Rusk's fellow Marines -- who tried to come near him. Rusk did not survive the assault, but Eli was granted early retirement so he could live with Rusk's family.