The Princess Royal has unveiled a memorial sculpture to the animals who have served and died alongside British and allied troops.
Princess Anne unveiled the sculpture of two mules.
The monument, in Park Lane, central London, depicts two mules, a horse and a dog, together with lists of the numbers of animals lost in conflicts.
It honours all animals used in war, including horses, dogs, dolphins, elephants, pigeons and even glow worms
A batch of pigeons was released as part of the unveiling ceremony on Wednesday.
The monument pays special tribute to the 60 animals awarded the PDSA Dickin Medal - the animals' equivalent of the Victoria Cross - since 1943.
They include 54 animals - 32 pigeons, 18 dogs, three horses and a cat - commended for their service in World War II.
Among these heroes were:
Rob, a para-dog who made more than 20 parachute drops while serving with the SAS on top-secret missions in Africa and Italy.
Ricky, a canine mine-detector who continued with his dangerous task of clearing a canal bank in Holland despite suffering head injuries.
Images of animals used in various conflicts are also included.
Winkie, a pigeon that flew 129 miles with her wings clogged with oil to save a downed bomber crew.
Mary of Exeter, another pigeon, which flew back with her neck and right breast ripped open, savaged by hawks kept by the Germans at Calais.
Search and rescue dogs, Beauty, Peter, Irma and Jet, who located survivors
buried in the debris of the London Blitz.
Metropolitan Police horses, Olga, Regal and Upstart, who faced their fear of
fire and the hail of flying bombs.
More recent recipients include Buster, a six-year-old Springer spaniel, who won it for his service in Iraq in 2003, when he discovered a hidden cache of explosives in
the southern city of Safwan.
The memorial, at Brook Gate, was designed by sculptor David Backhouse and carved from Portland stone, with bronze relief of different animals.
The inscription reads: "Animals In War. This monument is dedicated to all the animals that served and died alongside British and allied forces in wars and campaigns throughout time.
"They had no choice."
Mr Backhouse told BBC News: "I don't think anyone can fail to be moved by the stories of pigeons that struggled home and dogs that came through under fire and the service some of the mules in particular gave, the amount of time they served.
"Whether you can call an animal a hero I don't know but they certainly did extraordinary work for their masters."
Animals in war
Horses - Eight million killed in WWI alone, carrying men, arms and supplies into battle
Pigeons - 200,000 used as messengers in WWII. Of 17,000 parachuted into enemy territory, fewer than one in eight returned.
Dogs - used to hunt mines and search for the wounded. Still routinely used today
Mules - used as transport in the Burmese jungle, with their vocal chords slashed to keep them quiet
Camels, oxen and elephants - used for similar purposes elsewhere
Dolphins and sea lions - used today to find underwater mines and protect ships
Glow worms - used in WWI as an aid for map reading
Former mountain gunner Col John Andrews, 80, of Winchester, Hampshire, attended the unveiling in memory of mules who helped during his time in the jungle in Burma in 1944.
"My life was saved by the mules. The only way we could get the guns up to us was using them.
"There was no way we could do anything else," he said.
PDSA director general Marilyn Rydstrom said the memorial was "the nation's long-awaited and very welcome tribute" to the animals.
"It will also stand as a testament to the extraordinary bond that animals share with mankind in times of extreme adversity."
The PDSA - People's Dispensary for Sick Animals - is a charity providing free veterinary care for animals whose owners cannot afford private vets' fees.