Until a 2000 law allowed them to be adopted, many of the dogs that served with U.S. soldiers were euthanized by military veterinarians, The Denver Post reported.

Most of the more than 4,000 dogs that served in Vietnam died there. Some were killed by enemy troops, some died of tropical diseases, and some were put down by military veterinarians or given to the South Vietnamese army, the Post reported.

"The day we stood down in 1972, (Gen. William) Westmoreland was pinning medals on us as I watched the South Vietnamese take our dogs away," Rick Claggett of Denver, who worked with a German shepherd named Big Boy, told the Post. "Today, talking about this, I still choke up. The government shouldn't have let this happen."

Claggett is a member of the Vietnam Dog Handlers Association, which is lobbying Congress to approve the war-dog memorial.