What does it mean to be a game changer? It means that after the introduction of this weapon, armies and battlefields had to fundamentally change how they fought in order to overcome it. There are many inventions that helped soldiers do their job better, but only a few that changed warfare at its core. They changed the way wars are fought, the way battles and battlefields develop, and how commanders plan their strategies. Here are 13 weapons that were game-changers.

For this list, we will include only weapons, not tools or technology that, while revolutionary and game-changing, were not used to directly kill people. This includes things like radar, GPS, the stirrup, fortified walls, trenches, barbed wire, and so on.

Of course, this won’t include every single weapon that changed warfare, for each period of history and every continent had their own weapons that changed their game of war. We will include only a few of the most impactful.

#1 Cavalry

Nothing in the history of warfare and of humankind has been as impactful as the domestication of the horse. No military innovation since has surpassed the impact the horse had on the battlefield. From the introduction of the cavalry soldier onto the battlefield thousands of years ago, as far back as 1,550 BCE, all the way to World War I, the fastest and most lethal weapon system on the battlefield was a man on a horse.

Given the difficulty of raising, training, and keeping horses, along with training soldiers to ride them effectively, most ancient cavalry forces were limited to chariots. However, the true rise of cavalry on the battlefield was developed by the nomads of the Eurasian Steppe: the Iranic Parthians, Sarmatians, Scythians, and later the Mongols, among many others. So powerful was the role of horse archers on the battlefield that steppe tribes remained a significant threat to their neighbors until the 1800’s.

European armies didn’t implement large cavalry forces until the late Middle Ages, and even then, the soldiers would mostly dismount before entering combat. Europe lagged behind most of the world in combat innovation and effectiveness until relatively recently.

#2 Airplane

Immediately after its invention, the airplane was adapted to be a weapon of war and it forever changed the way soldiers thought about the battlefield. No longer did they have to just worry about the enemy in front of them, they had to keep an eye on the sky, too.

Fighters, interceptors, bombers, and reconnaissance planes made their big entrance during World War I, which was the stage for many weapon innovations.

Suddenly, front lines didn’t seem so well-defined, as airplanes flew over the chaos and could drop bombs or shoot at important targets far behind what was once an impenetrable wall of trenches and barbed wire. New technology had to be invented to defend ground-based targets against airplanes and to attack targets in the air. The flurry of technological progress that occurred in response to the introduction of the airplane changed the battlefield more quickly than almost anything else in history.

#3 Artillery

Every time the defenses of a city grew stronger, the tools for knocking down or overcoming those defenses improved. Siege weapons of various types have been employed as long as there were walls to tear down, but none had such an impact as the cannon artillery.

Artillery in the form of mortars has been around since about the 9th or 10th century CE, but they were large, cumbersome, difficult to use correctly, and dangerous to use. It wasn’t until the 1400s when artillery became much more powerful, the barrels longer, and the construction more reliable and safer that artillery became a regular sight on the battlefield. Typically, during a siege, the defending side has a significant advantage over the attackers. With the introduction of the cannon and mortar, that advantage turned to the attacking army.

The difference came in that gunpowder artillery was able to completely demolish walls and accurately hit targets within the city. Mehmet the Conqueror was able to take Constantinople in 1453 when his artillery destroyed the legendary walls of the city. Castles, forts, and cities with large stone walls soon became prisons if cannons were brought to bear. Armies were now incentivized to fight outside a city instead of retreating within the walls for safety.

#4 Hand-held firearms

Like the crossbow that came before it, the hand-held firearm revolutionized the battlefield because it allowed untrained, unskilled people to become deadly forces of destruction.

However, unlike the crossbow, which was banned in some parts of Europe because it was unsporting and broke the rules of chivalry, the hand-held firearm changed the landscape of the battlefield so drastically that any nation that wanted to compete militarily was forced to adopt firearms into their armies.

After their usefulness was demonstrated in battlefields from Asia to Europe, armies quickly learned how best to use guns instead of bows and hand-held weapons. For the first time since pre-history, the most effective killing tool was not a sword or a spear or arrowhead. Every innovation and change to the hand-held firearm ever since simply built upon the monumental game-changer that was the first gun.

#5 Warships

Naval warfare has been just one aspect of wars that were exclusively fought on land for most of human history. When battles did happen at sea, it was usually between ships that carried troops who fought just as they would on land, but on flat barges and decks instead. Ramming was a common tactic, then boarding and anti-boarding tactics. The only reason naval warfare happened at all was simply because it was a useful way to transport troops long distances, not because it was useful in any meaningful way.

That all changed with the introduction of ships that could both transport troops and defend themselves without soldiers, archers, or marines. It began with loading cannons on ships before the advent of the Age of Sail, and soon large ships became the determining factor of land battles. They controlled trade, stopped armies from retreating by sea, blockaded cities, and starved empires into surrender. Commanders couldn’t wage an effective war by ignoring the sea anymore as they had for millennia beforehand. Ignoring the power of ships was a quick way to lose a war. As the size of empires expanded to include multiple oceans and seas, the landscape of the battle became ever more blue.

#6 Rifled Muskets

The adoption of the hand-held firearm forced armies to abandon plate armor and swords and adopt massed infantry firing lines. The musket was powerful and easy to use, but it was inaccurate. The only way to ensure that enough shots hit your enemy to force them to retreat was to fire many muskets at the same time.

With the rifled musket, that tactic soon became a death wish. Rifled muskets, especially breech-loader rifles, had longer range and were much more accurate. Whereas typical formations only had time for a handful of shots before one side retreated, rifles could fire dozens of shots well before the other side was even in range to fire once. Armies soon abandoned the mass infantry tactic and adopted trench warfare and other tactics that didn’t put so many men in danger.

#7 Maxim Gun

Even with the introduction of the hand-held firearm, the look of the battlefield was still relatively unchanged. Large armies marched in open fields against each other, opening fire before engaging in hand-to-hand combat. Even with guns grenades and cannons, the battlefield would still be familiar to an ancient Assyrian. With the introduction of the Maxim gun, that was no longer the case.

The Maxim gun was the first fully automatic machine gun in the world, invented in 1884. It is called the “weapon most associated with imperial conquest” and was the primary tool used to conquer and subdue other countries by the colonial powers. It was used during the Russo-Japanese War, World War I, World War II, and beyond. It was the predecessor to modern machine guns.

Its impact was just as much physical as it was psychological. Armies could not march against each other in rank and file to do battle without being obliterated by a single Maxim gun. Warfare retreated to trenches, artillery bombardments, and large-scale assaults. Squad warfare began to develop during this time, presenting smaller targets to Maxim gun emplacements and diminishing their impact on the battlefield. Never again after the introduction of the Maxim gun would armies march against each other in open fields.

#8 Chemical Weapons

Biological warfare has been a common feature of warfare since ancient times. Poisoning wells, catapulting decaying bodies into cities, and releasing sick prisoners were all examples. Chemical warfare, however, didn’t begin until World War I with the introduction of chlorine gas.

In 1915, German soldiers opened almost 6,000 canisters of the poisonous gas at the Ypres battlefield in Belgium. There were 7,000 total casualties, of which 350 died. Chlorine gas was terrifyingly lethal in almost every way: it was cheap, it was easy to deploy, it was heavier than air so it would sink into enemy trenches, and all it took was one inhale to kill enemy soldiers.

Both sides began to develop and deploy even more lethal and deadly gasses throughout the war. One of the gasses, phosgene, was entirely odorless and responsible for around 80% of the gas-related fatalities during the war.

How did this change warfare? Today, no soldier enters any battlefield without the equipment and the training to deal with chemical warfare. Soldiers can no longer plunge head-long into an abandoned enemy position for fear they might have left behind undetectable chemical weapons ready to kill whoever sets them off.

Chemical weapons were banned by the Geneva Convention after World War I, but that hasn’t stopped countries from using them, including the United States, Iraq, Syria, and other dictatorships. During the U.S. invasion of Iraq, U.S. soldiers used a combination of white phosphorus and explosives they called “shake ‘n’ bake”. The white phosphorus produces phosphorus pentoxide smoke that burns on contact with moisture and causes severe eye burns and permanent damage. They killed women and children during the massacre in Fallujah.

When it comes to holding on to power or letting a foreign power conquer your country, it is doubtful most world leaders would resist deploying chemical weapons.

#9 Tanks

Many similar lists will include tanks, but they miss the point of why. Why were tanks such an important innovation and how did they actually change warfare? There were motorized vehicles in war long before the tank was invented. Trucks and cars had been used for years filling the role of cavalry where horses were in short supply. The answer to this question is simple: it was the only vehicle that could reliably traverse the barbed wire and trenches of no-mans-land in World War I, withstand the fire of machine guns, and reach the other side with enough firepower to actually fight.

Tanks were initially used as infantry support, but their true potential was finally realized when fully mechanized tank divisions fought together, blazing through enemy defenses that would tear soldiers apart and pursue fleeing soldiers before they had time to set up another defensible position.

Tanks are still used today in the same manner: a spearhead pushing through enemy defenses or obstacles for infantry to secure an area.

#10 U-Boat

The submarine has existed ever since the 1700s, but the technology really took off during the 1800s. Yet they had no significant impact on warfare until the 20th century. The reason the German U-boat was so much more successful than previous versions, and even contemporary versions in greater numbers, was a combination of technology and innovative submarine tactics developed especially for submarine combat. The unprecedented success of German U-boats highlighted the changing state of war on the oceans, and the need to develop new weapons to engage with submarines. Submarines were the most effective anti-ship weapon used by the United States during World War II and destroyed over 60% of the Japanese merchant fleet and destroyed more ships than all other weapons (on land, air, or sea) combined.

The advancement of stealth technology allows modern submarines to remain a hidden and ever-present threat to every navy.

#11 Aircraft carrier

Naval warfare was always a competition of who had the biggest ships, the most ships, and who could keep them afloat the longest. It evolved from infantry combat aboard floating barges to a focus on large battleships through the 19th and early 20th centuries. World War II showed the world that the age of the battleship was over with the introduction of the aircraft carrier.

You will probably never see a large-scale ship battle ever again because of aircraft carriers. The ability to scout far in advance of a fleet and engage enemy ships from the air has made the aircraft carrier the dominant power of the seas. This point was made during the Battle of the Pacific in which aircraft carriers obliterated enemy battleships from far beyond the horizon. The United States’ focus on developing carrier technology is what helped them secure their hold over the Pacific and win the war.

#12 Strategic Stealth Bombers

Just as planes changed the battlefield when they first entered the scene, strategic stealth bombers changed the game by refusing to participate. While everyone else is playing checkers, stealth bombers never showed up to the party and instead drop a bowling ball on the table during a video call.

Bombers, even high-altitude bombers, are vulnerable to enemy aircraft and anti-air weapons. Heavy armor, fighter escorts, and powerful guns help them stay in the air long enough to drop their bombs and come home. But it is hard to defend against an enemy you can’t see and is already halfway home by the time the bomb hits you. There is no real defense against a stealth bomber that is already overhead.

The introduction of strategic stealth fighters has forced armies to adapt to an enemy that can strike them nearly from space without being seen. Large armies cannot muster and march together without presenting a large target. Large military bases are no longer safe. Small squads must rely on concealment and camouflage in order to avoid detection and continue fighting.

The significant cost of the stealth bomber makes its use rare.

#13 Atom bomb

What could be more game-changing than a weapon that replaces the game you’re playing with an entirely different game? What could be more different from ancient warfare than a war that isn’t fought at all? Whatever the moral and ethical questions surrounding the atomic, and later nuclear, bomb might be, there is no arguing that the way we fight wars is forever changed as long as there is even one still around somewhere.

The ability to obliterate not only an army, but entire cities or a country in a moment finally made world powers hesitate before going to war. The Cold War was only the first of what will probably be many dangerous stand-offs in the future. Wars between powerful states are no longer fought on the battlefield but have been forced into the digital realm and live out in proxy wars. Nobody knows what will happen if the armies of the world powers ever do meet in open conflict, and world leaders are even less eager to find out.

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