The ol’ reliable military flak jacket. Many military veterans who served in the Vietnam War in 1955 would be no stranger to these flak vests due to the large number of mines that were planted by both sides to prevent quick advances by infantry troops, much like the North Vietnamese used during the First Indochina War.

In general, troops would wear military flak jackets to protect themselves from high explosive weapons such as mines, grenades, anti-aircraft artillery, and even some variation of shotgun ammunition that would have their case fragments (frags) blow soldier’s socks off in a blink of an eye. A single slim sliver of metal from a mortar round the size of a toothpick entering your heart will kill you, and has.

U.S. Army soldier wearing a military flak jacket, Vietnam, 1971 (Wikimedia Commons). Source:
US Army soldier wearing a military flak jacket, Vietnam, 1971 (Wikimedia Commons)

Yup, the military flak jacket, protecting our military men since the 1860s. Wait, what? You might be asking yourselves, were there flak jackets in the Civil War? I thought they only had bulletproof vests! For all of you history buffs, sit back and let us take you through a bit of a blast to the past, no pun intended, of course.

Are Flak Jackets, Bulletproof Vests, Kevlar All The Same?

The military veterans reading this would probably get a laugh out of this question, but let’s face it, not many people know what the difference is between flak jackets, bulletproof vests, and kevlar. So to all our military guys out there reading this article, if you ever encounter someone asking about the difference, we think it’s best that they’re informed!

Now, for those confused about the difference, this might stem from the fact that people often interchange these three terms. Even video games sometimes list these gear as the same thing! So don’t be ashamed if you’re only finding out now. It’s really something that everybody seems to get wrong the first time around.

Let’s take you through the basics.

Kevlar seems to be the most searched body armor that pops up whenever you do a google search. So it may surprise you (or not) that Kevlar, the synthetic fiber itself, was made by American Chemist Stephanie Kwolek for DuPont in 1965. Simply speaking, Kevlar is the material or component used in making soft-body armor, which is different from a flak jacket. It was first used for racing tires, but they discovered that it could be used in the body protection industry because of its high tensile strength to weight ratio, making it 5 times stronger than steel.
The Improved Outer Tactical Vest (IOTV) used by the US military (Wikipedia/Wikimedia Commons)

Kevlar is what the military uses to make its bulletproof vests, combat helmets, and even as spall liners in armored vehicles. Most notably, the Nimitz-class aircraft carriers use Kevlar to reinforce certain areas of importance. It’s thinner and lighter than flak jackets and is mostly used by firefighters due to their high heat resistance and police officers (even SWAT) for body armor. It’s a common misconception that bulletproof vests stop all types of bullets, so it’s best to call them “bullet-resistant” as there are subcategories of ballistic vests with specific uses, most likely according to the type of ammunition it would stop.

What About Military Flak Jackets?

On the other hand, military flak jackets were first used during the 1860s. Technically, they were not flak jackets as these were just American Civil War soldiers putting steel plates in the pockets of their vets, but nonetheless, this was the start of the usage of what was to be known as flak jackets. Most of these earlier vests look like those armor you’d see from medieval times, specifically the one made by the Atwater Armor Company.

While there were attempts to make a bulletproof vest and flak jackets in World War I, it wasn’t until World War II that the term “flak jacket” would arise. The British noticed that they needed to protect their Royal Air Force (RAF) crew from flying debris (colloquially known as “flak“) that the Germans were firing against them through the “Fliegerabwehrkanone” or literally translated as “aircraft-defense gun.” This was for two reasons. First, everyone on the crew had an important job to do in terms of keeping the aircraft flying. The loss of the pilot and co-pilot to splinters or fragments of metal would doom the entire crew of a bomber as well.  The other reason was that these bombing missions could mean 12 hours of flying time with very limited medical care available to a wounded crewman.  Get hit on the way to the target and the bomber is not turning around and going back to base to get you stitched up, your plane is going to drop its bombs no matter what.  They would try to bandage your wounds and hit you up with morphine, but you might be looking at 10-12 hours before an actual doctor could treat your wounds.  A lot of flight crewmen were dying like that too.

In 1943, Colonel Malcolm Grow, an American US Eighth Air Force Surgeon serving in Britain, thought he could make a light armor that could prevent troops’ wounds, an idea that came to him while treating airmen. Thus, the first flak jacket was born, the “M1 Flyer’s Vest “… at 22lbs.

B-17 Flying Fortress Waist Gunner holding his damaged M1 Flyer's Best (left) (U.S. Army via Office of the Command Historian). Source:
B-17 Flying Fortress Waist Gunner holding his damaged M1 Flyer’s Best (left) (US Army via Office of the Command Historian). Source:

However, many pilots and airmen complained that the flak vest was too bulky for them, too heavy too! So the RAF gave them to the United States Army Air Force, which didn’t really like them either.  Bombers were made to carry fuel and bombs, crew spaces were very tight, and cramps.  USAAF crews were already wearing electrically heated thermal suits, with overalls, jackets, gloves, and boots made of heavy wool shearling, since it was twenty below zero in at 25,000 feet. Additionally, they also wore a parachute and a Mae West life jacket and now they were supposed to add a 22lb flak vest and helmet too?   You could barely move, let alone make it to the escape hatch to bail out if the plane was hit and burning. Crews tended to put them under their seats as splinter protection or stand on them while manning waist guns. They might also don them just before the German AAA guns opened up and take them off as soon as they were out of range.  It also bare mention that the weight of fuel and bombs on a B-17 or B-24 was very carefully measured to the last ounce.  Adding flak vests to a B-17 crew of ten meant an additional weight of 220lbs that would be deducted from their fuel load on a mission. That amounted to nearly 40 gallons of gas.  The gas they would need to get back from Germany.  That 40 gallons represented about 12 minutes of flight time and twelve minutes could be the difference in making back over the English Channel or ditching in the English Channel, which was ice water cold.

Many troops complained about the heaviness of these flak jackets and would take them off, especially in hot, tropical climates such as Vietnam. However, it is important to note that there were significant improvements with the design of flak jackets throughout these years, with the  M-1952A Body Armor, Fragmentation Protective at 8.5 pounds being used by troops in the Vietnam War. Research in 1951 stated that in times of combat, troops didn’t notice the heaviness of their equipment and flak jackets, likely because of the desire to survive and adrenaline pumping in their veins.

So in a gist, flak jackets are designed to protect against anti-aircraft guns, land mines, grenades, and low-caliber weapons to an extent. They were never intended to absorb or protect against gunfire, which was why Kevlar and bulletproof vests were made. But, they both offer protection for troops, albeit in different ways!

In all honesty, the history of bulletproof vests and flak jackets is quite extensive! So if you want to learn more about them, let us know in the comments section below.