(CNN)A highly anticipated postage stamp collection honoring US military dogs was released Thursday.
The US Postal Service announced in February that one of this year's "forever" stamp collections will honor the "nation's brave and loyal military working dogs."
The stamps feature four breeds that commonly serve in the armed forces: German shepherd, Labrador retriever, Belgian Malinois and Dutch shepherd. The dogs are featured on top of a white star with a red or blue background.
Dogs have served in the US military since World War I, and an estimated 2,300 military working dogs serve on US bases worldwide. The dogs perform dangerous tasks alongside servicemembers, often using their noses and convenient sizes for searches and rescues.
"These military dogs and search-and-rescue dogs are putting themselves on the line. They're out in the front lines," Diane Whetsel, head of the Sage Foundation, which provides funding for medical services for military dogs, told CNN in 2011.
US war dogs are also honored in Holmdel, New Jersey with a memorial originally built to remember dogs who served in Vietnam.
"They're treated exactly like a soldier, in every way, shape and form," said Robin Ganzert, the president and CEO of the American Humane Association.