When humans go to battle, they're often joined by animals — military dogs, horses and even pigeons. These furred and feathered partners in the trenches save lives, sometimes while being injured or killed in the line of duty.

The British charity, the People's Dispensary for Sick Animals (PDSA) awards the Dickin Medal, considered to be the highest animal honor in the world. The organization says the medal is the animal equivalent of the Victoria Cross, the highest military decoration awarded for valor "in the face of the enemy."

So far, 29 dogs, 32 pigeons, four horses and one cat have been honored for "gallantry." The latest is Lucca, the first U.S. Marine dog to receive the honor. Here are some of their amazing stories.

Lucca

Lucca dog in grassLucca lost a leg as a result of an IED explosion in Afghanistan. (Photo: PDSA)

The most recent recipient of the Dickin Medal, Lucca completed 400 missions in her six years with the U.S. Marine Corps in Afghanistan. The search and rescue dog was at the front of patrols with her handler and is credited with protecting thousands of troops. On her last patrol in March 2012, an IED exploded, resulting in the loss of one of her legs. Lucca is now retired and lives with her handler, Gunnery Sgt. Christopher Willingham and his family in California. "Lucca is very intelligent, loyal and had an amazing drive for work as a search dog. She is the only reason I made it home to my family and I am fortunate to have served with her," Willingham says. "Today, I do my best to keep her spoiled in her well-deserved retirement.” Lucca received the medal in April 2016, the first U.S. Marine Corps dog to receive the award.

Bob

first Dickin Medal recipient, BobThe first Dickin Medal recipient was Bob, a mixed-breed dog. (Photo: PDSA)

Bob, a mixed breed, was the first to receive the Dickin Medal in March 1944. He was traveling with his unit in North Africa when he suddenly froze and refused to move. The perceptive pooch saved lives because the enemy was close by. Because of Bob's actions, the men in his unit remained unharmed.

G.I. Joe

Dickin Medal winning pigeon GI JoeG.I. Joe was noted for his heroic work in the United States Army Pigeon Service during World War II. (Photo: PDSA)

A member of the U.S. Army Pigeon Service, G.I. Joe was credited with making the most outstanding flight in his division in World War II. Joe flew 20 miles in 20 minutes, carrying a message that arrived just in time to save the lives of at least 100 Allied soldiers.

Diesel

Diesel the French police dogDiesel was a 7-year-old Belgian Malinois and part of an elite French anti-terrorism unit. (Photo: Police Nationale)

Diesel, the now-famous police dog killed leading a police raid on a terrorist cell in Paris in November, was honored posthumously. The Belgian Malinois was part of the elite French Research, Assistance, Intervention and Deterrence unit. He was part of a siege on a suburban apartment targeting terrorists involved in the Nov. 13 Paris attacks. Diesel was sent into an apartment ahead of officers, where police say he was shot and killed by terrorists, likely saving the life of his handler. His death inspired the hashtag #JeSuisChien ("I am dog") on social media across the globe.

"As guardians of the world’s most prestigious animal awards programme, we were inundated by messages from members of the public to recognise his heroism," said PDSA Director General Jan McLoughlin, on awarding the medal in December 2015. "The PDSA Dickin Medal recognises conspicuous devotion to duty in the theatre of conflict and Diesel is a truly deserving recipient. His gallant actions helped to protect human life in the face of imminent danger, and we are very proud to honour him in this way.”

Broad Arrow and Maquis

pigeons Broad Arrow and MarquisPigeons Broad Arrow and Maquis were honored for delivering messages during WWII. (Photo: PDSA)

Messenger pigeons Broad Arrow and Maquis were awarded the medal in 1945 for delivering three important messages during WWII. The were part of Britain's National Pigeon Service, a volunteer civilian organization.

Olga, Regal and Upstart

Dickin Medal winning horses Olga, Regal and UpstartOlga, Regal and Upstart with their handlers at the Dickin Medal ceremony in 1947. (Photo: Fair Use/Wikipedia)

Four horses have received the Dickin Medal and that includes Olga, Regal and Upstart who were honored April 11, 1947, and Warrior who was awarded an honorary posthumous medal in September 2014. The horses were all members of London's Metropolitan Police Service. Olga and Upstart were honored for courage during active duty, and Regal was honored for staying calm while his barn was bombed two separate times. Warrior's honorary medal was awarded on behalf of all animals that served in WWI.

Rip

Rip, Dickin Medal winning dogAir Raid Precautions dog Rip sits on top of a pile of brick rubble and timber following an air raid in London. (Photo: Ministry of Information/Wikimedia Commons)

A stray picked up by an air raid warden, mixed-breed terrier Rip became a search and rescue dog during heavy bombing of London during WWII. He was credited with saving the lives of more than 100 people.

Simon

Simon the cat, Dickin Medal winnerSimon the cat kept the crew's morale up while keeping the rat population down on the HMS Amethyst. (Photo: PDSA)

Only one cat ever received the award for bravery: "or keeping the crew's morale up and the rats down." Simon was smuggled aboard the HMS Amethyst of the Royal Navy by a 17-year-old seaman who found the malnourished kitty wandering the dockyards of Hong Kong. The black-and-white cat soon became a favorite onboard, protecting their food from a rat infestation and snuggling up to the crew. Bob survived injuries from a cannon shell but sadly died in quarantine shortly after returning home.

Khan

Khan Dickin medal dogKhan received the Dickin Medal after he saved his handler from drowning. (Photo: PDSA)

Khan the German shepherd saved his handler, Lance Corporal James Muldoon, from drowning when their ship capsized during WWII while under heavy fire. Muldoon couldn't swim, so Khan pulled the soldier more than 200 yards through the water onto the shore to safety before collapsing next to him.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.