0:02 overpriced, over complicated, and as a
0:04 cherry on top, a death trap. Why was
0:06 this tank developed with aluminum armor,
0:08 a missile launcher instead of a gun? And
0:10 why did military planners want to drop
0:12 it straight into combat from a plane? It
0:14 saw heavy action in the Vietnam War,
0:15 where it earned a dark reputation that
0:17 quickly pushed it out of frontline
0:19 service. In the end, it became nothing
0:21 more than a target so others could
0:23 practice shooting at enemy tanks. You're
0:25 about to see all of that, as well as the
0:27 dark reason why so many Sheridan crews
0:29 never made it out alive.
0:31 During and after the Second World War,
0:33 development of tanks was huge and
0:34 militaries went into full
0:36 experimentation mode with various
0:38 concepts to find the right balance
0:40 between protection, mobility, and
0:42 firepower. So, they ranged from absurdly
0:45 heavy like the T-28 Super Heavy tank, a
0:48 95 ton armored bunker with four sets of
0:49 tracks, all the way to something like
0:52 the M56 Scorpion, basically a recoilless
0:54 rifle on a paper thin chassis with no
0:57 armor for the crew. Now, every one of
0:58 these aspects comes with its pros and
1:00 cons, and if you could find exactly the
1:02 right spot between those three main
1:04 characteristics, you would probably have
1:06 the best tank in the world. However, as
1:08 we're about to see, in trying to achieve
1:11 exactly this, the M551 Sheridan would
1:13 end up having almost the cons of each
1:15 characteristic, and you're now going to
1:18 see why. In the early 1960s, when all
1:20 major powers were working on heavier and
1:22 heavier main battle tank concepts,
1:24 someone got the idea to instead create a
1:25 heavily armed tank that could be dropped
1:28 by parachute exactly where needed on the
1:30 battlefield. While the Soviet Union
1:32 focused on massive armored spearheads in
1:34 their doctrine, the US turned to air
1:36 mobility and rapid deployment, trying to
1:37 build lightweight forces that could be
1:40 flown in anywhere. Military planners
1:41 wanted something that could be delivered
1:43 together with airborne units and provide
1:45 them support in their most vulnerable
1:47 moment while they were lightly armed
1:48 behind enemy lines as they couldn't
1:50 parachute heavy equipment with them.
1:52 This was observed in multiple actions
1:54 where paratroopers had to fight against
1:56 heavy enemy armor using only a couple of
1:58 light anti-tank weapons they could bring
2:00 with them. There was actually the M22
2:02 Locust that could be delivered into
2:04 battle by glider, but it had only a 37
2:07 mm gun and practically no armor.
2:08 However, this idea was pretty much put
2:11 on hold during the Cold War until after
2:13 some time in the moment when main battle
2:16 tanks like the M48 and M60 patterns took
2:18 all the attention. The US Army suddenly
2:19 wanted to create a tank three times
2:22 lighter. That is thanks to the emergence
2:25 of the Soviet PT76, which showed the US
2:26 that they didn't have anything remotely
2:28 like it. It was fully amphibious,
2:30 lightly armored, able to cross water
2:32 without engineering support. Even worse,
2:34 the North Vietnamese army had them, as
2:36 it would turn out, and they were using
2:38 them in terrain where American tanks
2:40 couldn't quite follow. Then, being
2:42 classified under the name armored
2:45 reconnaissance vehicle, the M551 began
2:46 to take shape, using an aluminum hull
2:48 and a lightly armored steel turret as
2:51 its protection. Aluminum was used to
2:52 keep the weight down while still
2:54 providing protection against 50 caliber
2:56 rounds. The idea was that aluminum is
2:58 lighter, so it could be used in thicker
2:59 plates to match the same protection as
3:01 thinner steel plates, but at a lower
3:04 weight. However, it had a much lower
3:06 melting point than steel, which didn't
3:07 go well with high explosive anti-tank
3:10 type weapons like RPGs and blasts from
3:12 mines. As it would quickly turn out,
3:13 getting hit by anything bigger than
3:15 heavy machine gun meant a very bad day
3:18 for its crew crammed inside. However,
3:20 enemy fire would turn out to be only one
3:22 part of the problem. The other came from
3:24 the tank itself, and you'll see that in
3:28 a moment. Production began in 1966 with
3:30 Sheridans now weighing just over 34,000
3:32 lb, which was only about 4,000 lb
3:35 heavier than the M113 armored personnel
3:37 carrier that was entering service at the
3:38 same time and was envisioned to fight
3:41 together with Sheridans. The Sheridan
3:43 was manned by a commander, gunner,
3:45 loader, and a driver. Its diesel engine
3:48 gave it around 300 horsepower and very
3:50 good off-road capabilities with a top
3:53 speed of 45 mph. And most importantly,
3:54 they could be airlifted and delivered
3:56 directly to the battle when needed in
3:59 rapid deployments. Transport aircraft
4:01 like the C130 used a unique lowaltitude
4:04 parachute extraction system. The plane
4:05 would fly slowly just a couple of meters
4:07 off the ground, while a horizontally
4:09 deployed parachute would drag out the
4:10 tank and help stop it after it slid
4:12 across the ground. The crew would
4:14 parachute separately and then find and
4:17 mount their tank. Sheridan could also
4:19 cross water using flotation screens like
4:23 the duplex drive Sherman tanks on D-Day.
4:24 The most interesting thing about it,
4:26 however, was definitely its gun, which
4:28 operated completely differently from any
4:30 other tank main gun at the time.
4:31 Revolutionary, but a major part of the
4:33 Sheridan's dark reputation it was about
4:36 to earn in combat. The M81 was a low-
4:39 velocity smooth boore gun. actually a
4:42 missile system firing 60 lb caseless 152
4:45 mm shells. This concept was supposed to
4:47 help solve the problem of light vehicles
4:48 carrying heavy armorament. And in
4:50 theory, everything looked like they had
4:52 succeeded. In practice, however, it was
4:55 a different story. It could fire two
4:57 main types of ammunition, conventional
4:58 high explosive shells and a
5:00 revolutionary wireguided anti-tank
5:02 missile designed for longrange
5:04 tank-on-tank engagements. It could also
5:06 fire canister shots, turning the gun
5:08 into literally an enormous shotgun.
5:10 However, the first problems emerged
5:12 almost immediately. The recoil was
5:14 immense and it damaged the fire control
5:16 system and electronics. The problem was
5:18 also that the gun's short barrel and low
5:20 muzzle velocity made the shell
5:22 trajectories very high and slow, which
5:23 meant poor accuracy, especially at
5:26 longer ranges. The rate of fire and
5:28 reload was also painfully slow. Three
5:30 rounds per minute could be fired at best
5:32 by a well-trained crew, which is quite
5:34 bad when you compare it to around 17
5:35 rounds patents could fire in the
5:38 so-called mad minute. It could also
5:40 carry only 20 rounds, whereas Patns
5:42 again could carry over 50. Because of
5:44 the caseless rounds, the loader had to
5:45 wait for the mechanism to open and for
5:47 the air vents to clear the gun tube and
5:49 breach before loading another round. The
5:51 Chilea guided missile, which was
5:52 supposed to be Sheridan's signature
5:55 weapon, turned out to be almost useless.
5:57 Although it had a supposed range of
5:59 3,000 meters and a powerful warhead, it
6:01 needed a clear line of sight and no
6:02 interruption in its flight from the gun
6:04 toward the target or it would be thrown
6:07 off. After launching, the missile was
6:08 controlled by the gunner using a
6:11 joystick and guided onto the target. The
6:13 catch is that it didn't work under 800
6:14 yd and in the war it was about to be
6:17 deployed in, the Sheridan wouldn't fire
6:19 this revolutionary weapon, not even
6:22 once. Now, as the war in Vietnam began,
6:23 Sheridan wasn't immediately deployed
6:25 because the production of ammunition
6:27 hadn't caught up yet. In the beginning
6:30 of 1967, the first Sheridans were sent
6:32 to Vietnam to begin replacing M48
6:34 patterns. However, it would immediately
6:36 go wrong. Their light configuration was
6:38 good for difficult, muddy terrain. But
6:40 the slow and complex venting systems and
6:43 semi-automatic loaders were unreliable,
6:44 especially in the rough conditions of
6:47 Vietnam. Out of 74 first deployed
6:49 Sheridans in just the first 3 months,
6:51 there were 16 serious mechanical
6:54 breakdowns, 41 failed shots, 140
6:56 defective rounds of ammunition, and 25
6:59 burned engines. Then 125 turret
7:01 electrical faults, several recoil system
7:03 faults, and even instances of blown up
7:05 guns. They were sensitive to moisture,
7:07 heat, and rough handling, which is not
7:09 something you'd be in short supply of
7:11 during the war. Crews quickly learned
7:13 not to attempt to fire damaged shells.
7:14 They would also soon learn the hard way
7:16 that after being hit by basically
7:18 anything, you'd want to exit the tank as
7:20 soon as possible. Sheridan crews
7:22 suffered much higher casualty rates than
7:24 patent crews because they were often
7:25 assigned to reconnaissance and road
7:27 clearing missions. And in that role,
7:29 their aluminum armor, enemy fire, and
7:31 mines combined with shells that could
7:33 very easily ignite, were not exactly the
7:35 best combination in the world. You see,
7:37 the main body of the shell casing was
7:39 made of a combustible material designed
7:41 to burn up completely when fired. Only a
7:43 small metallic base stub remained which
7:45 had to be ejected manually after firing.
7:47 Now add to that the fact that ammo was
7:49 stored in unprotected racks between the
7:50 crew members inside the fighting
7:52 compartment. Just one month after
7:54 arrival in Vietnam, a Sheridan drove
7:56 over a mine which surprisingly
7:58 penetrated the light aluminum belly
8:02 armor and ignited the 152 mm shells. The
8:04 result was an immediate catastrophic
8:06 explosion with the unfortunate crew
8:08 still inside. And it wasn't the only
8:11 case. Soon after, nine Sheridans were
8:13 crossing a river. Three hit mines and
8:15 were also completely destroyed. In
8:17 another instance, nine Sheridans were
8:19 destroyed by RPGs in a single
8:21 engagement. Very soon in the war, the
8:23 sight of a completely blownup Sheridan
8:25 became concerningly common. They would
8:27 burst into flames immediately after
8:29 being hit by anything, and it started to
8:31 look like a new Tommy Cooker, just like
8:33 the Sherman tank in World War II before
8:35 they introduced wet ammo stowage.
8:37 Sheridan, on the other hand, didn't have
8:39 it. Crews tried to protect themselves as
8:41 always, adding additional plating and
8:43 sandbags, but nothing could solve the
8:45 fundamental mistakes in the tank's core
8:47 design, and it very quickly became very
8:49 unpopular among crews. Sheridan began to
8:52 be replaced already in 1978, although
8:54 there was no real replacement for a
8:56 rapidly air deployable tank in sight at
8:58 the moment. Some were later upgraded to
9:01 the A1TS model. A few saw action in the
9:03 Panama invasion in 1989. 10 were
9:05 delivered using the airdrop technique
9:08 with the C141. One of which had a
9:09 parachute failed to deploy and got
9:11 destroyed and another one was damaged.
9:14 This marked the first and only combat
9:16 airdrop of tanks in history. They were
9:17 then used in the Gulf War in the first
9:19 phase of the operation before heavy
9:21 armor arrived by ship. They saw some
9:23 tank-on-tank combat, but due to their
9:25 armor and age, they were mostly used as
9:27 reconnaissance. Just six Shellar
9:30 missiles of over 80,000 produced were
9:32 recorded as having been fired in combat.
9:34 By the late 1980s and early '9s, the
9:36 Sheridan wasn't trusted to fight real
9:39 wars anymore. Some were converted and
9:41 used to simulate Soviet armor for
9:42 training. They became the so-called
9:45 opposing force units. In other words,
9:46 pretending to be the bad guy so real
9:48 tanks could practice blowing it up,
9:50 which frankly wasn't very hard. Target
9:52 practice wasn't quite the glamorous end
9:54 for a tank that cost about 12 billion to
9:56 develop in today's equivalent. If you
9:58 found this story interesting, you might
