Here are some of the ways horses have been used in wars and conflicts. Millions upon millions have died. They didn’t give their lives. The lives were taken.

A draft horse shown left hitched to a post, his partner just
killed by shrapnel, 1916
Originally known as Decoration Day, Memorial Day originated in the years
following the Civil War and became an official federal holiday in 1971.
Here are some of the way horses have been used in wars and conflicts.
Millions upon millions have died for it. They didn’t give their lives. The
lives were taken.
American Civil War
More than 1,000,000 horses and mules were killed during the U.S. Civil
War. In the early days of the conflict, more horses than men were killed.
Just at the July 1863 Battle of Gettysburg alone, the number of horses
killed was about 1,500—881 horses and mules for the Union, and 619 for the
Confederacy.
Eric J. Wittenberg, the award-winning Civil War historian, writes:
During the era of the Civil War, 1861-1865, there were no internal combustion engines fueled by gasoline, so there were only three ways to transport men, equipment and supplies: by boat, by train, or by horse. Horses were the primary means for logistics. Horses were used by artillery, by cavalry, by infantry, and by teamsters to move men and equipment.
WW I
Horses and mules provided the overwhelming majority of the power used to move men and machines – the true “horsepower” of the war effort. They served in a wide variety of roles, including being ridden, as draft animals pulling vehicles and guns, and as pack animals.
Horses were in demand during the First World War. Britain responded to this
shortage by obtaining its horses by importing them from America and New
Zealand with as many as 1,000,000 coming from America. This costs Britain
67.5 million pounds. Germany had a more elaborate system before the war.
They had set up sponsored horse-breeding programmes in anticipation of the
war. Their horses were registered every year, just like army reservists.
The Central Powers, unlike the Allies, were unable to import horses from
overseas and as a result, led to their defeat through paralyses artillery
battalions and supply lines.
During the war, many horses died because of exhaustion, drowning, becoming
mired in mud and falling into shell holes. In some cases, riders were killed
and their horses captured. Horses were sometimes fed and cared for poorly,
poison gas attacks injured their respiratory systems and skin, and skin
conditions such as mange were common. The invention of improvised nose
plugs, however, served to help horses in the event of a gas attack. Improved
gas masks were later on created by both the central and Allied nations,
although most of the horses destroyed them mistaking them for feed bags.

The War Horse is a memorial to the Civil War horse, designed by Tessa
Pullan of Rutland, England, and given to the historical society by Paul
Mellon.
In 1917, when more than 94,000 horses were sent from North America
to Europe and 3,300 were lost at sea. Around 2,700 of these horses died when
submarines and other warships sank their vessels.
Eight million horses and countless mules and donkeys died in the First World
War. They were used to transport ammunition and supplies to the front and
many died, not only from the horrors of shellfire but also in terrible
weather and appalling conditions.
WW II
OliveDrab.com writes:
World War II was the first highly mechanized war, and the most vivid images
of the war include tanks, long convoys of trucks and jeeps, masses of
bombers flying over. But there were still large numbers of horses and mules
employed as cavalry, field artillery draft animals, and in supply trains.
The United States was the most fully mechanized, but even the U.S. used
animals throughout the war.
When mobilization for World War II began in 1939, it was predicted that the
Army would need 200,000 horses. In 1940, mechanization of the Army was well
under way, but the Army still had two horse cavalry divisions (the 1st and
the 2d), two horse-drawn artillery regiments, and two mixed horse and motor
transport regiments, with a total authorization of 16,800 horses and 3,500
mules.
The National Interest website tells us that:
By 1939 the German Reich possessed 3,800,000 horses while 885,000 were
initially called to the Wehrmacht as saddle, draft, and pack animals. Of
these, 435,000 horses were captured from the USSR, France, and Poland.
Additional horses were purchased from Hungary, Romania, Czechoslovakia, and
Ireland.
Nearly 3 million horses and mules were used by the Germans During World War
II. Of these an estimated 750,000 were killed.
The German Army entered World War II with 514,000 horses, and over the
course of the war employed, in total, 2.75 million horses and mules; the
average number of horses in the Army reached 1.1 million.
Though the US army dispensed with horses by 1943 the Nazis embraced them,
employing 2.7 million during the Second World War. Almost two-thirds were
killed or wounded.
Still, it is estimated 1.75 million horses were killed during World War II,
although it could be as high as 2 million. Another report says the death
count may be as high as 5 million.
Hitler and Lipizzaner Horses
The following is a fascinating side story to World War II an horses. We found it in the New York Post, August 20, 2016:
The valuable Lipizzaner horses — snow-white and blue-black, many of them
Olympic dressage champions — had been stolen from the countries that the
Nazis occupied during the war. In addition to gold, jewelry and artwork, the
Nazis seized the valuable horses from Poland, Yugoslavia, Italy and Austria.
The Nazis’ goal, according to author Elizabeth Letts in her new book “The
Perfect Horse” (Ballantine), was to breed the Lipizzaner with German horses
in order to create an equine specimen that was worthy of the German master
race.
Horses were central to the Nazi propaganda effort, and Hitler was often
shown as “the man who put Germany back in the saddle,” according to Letts.
In fact, as soon as he ordered the invasion of Poland in September 1939 and
unleashed the grisly chain of events that plunged the world into war, Hitler
had important plans for the country’s horses. As Letts writes, “In the
blueprint forged for its occupation, a plan was put into place for the
‘rebuilding of Poland’s horse-breeding industry’ for the ‘interest of the
German nation.’ ”
We found more, this time in an English newspaper.
Just as Hitler wanted to eliminate ‘impure’ human strains so Rau planned to use selective breeding to erase the individual differences characterising the several strains of Lipizzaner that had emerged and replace them with a single mould: pure, imperial and ideally suited to military use. [Source: Mission to rescue Hitler’s equine master race; Daily Express UK, 6 Aug 2016.]
Korean War — Sgt Reckless
You were waiting for her, right?

Korean War Veteran, Sgt Reckless.
Staff Sergeant Reckless (c. 1948 – May 13, 1968), a decorated war horse
who held official rank in the United States military, was a mare of
Mongolian horse breeding.
Out of a race horse dam, she was purchased in October 1952 for $250 from a
Korean stableboy at the Seoul racetrack who needed money to buy an
artificial leg for his sister.
Reckless was bought by members of the United States Marine Corps and trained
to be a pack horse for the Recoilless Rifle Platoon, Anti-Tank Company, 5th
Marine Regiment, 1st Marine Division.
She quickly became part of the unit and was allowed to roam freely through
camp, entering the Marines’ tents, where she would sleep on cold nights, and
was known for her willingness to eat nearly anything, including scrambled
eggs, beer, Coca-Cola and, once, about $30 worth of poker chips.
Reckless served in numerous combat actions during the Korean War,
carrying supplies and ammunition, and was also used to evacuate wounded.
Learning each supply route after only a couple of trips, she often traveled
to deliver supplies to the troops on her own, without benefit of a handler.
The highlight of her nine-month military career came in late March 1953
during the Battle for Outpost Vegas when, in a single day, she made 51 solo
trips to resupply multiple front line units.
She was wounded in combat twice, given the battlefield rank of corporal in
1953, and then a battlefield promotion to sergeant in 1954, several months
after the war ended.
Reckless also became the first horse in the Marine Corps known to have
participated in an amphibious landing, and following the war was awarded two
Purple Hearts, a Marine Corps Good Conduct Medal, was included in her unit’s
Presidential Unit Citations from two countries, as well as other military
honors.