A common thread through human history is the constant development of deadly new combat technologies. The US Army and Bulletin of the Atomic Scientists have completed research on weapons used throughout history, using real-world data from battles to calculate their "lethality index," a numerical way to show how deadly each weapon can be that accounts for weapon range, rate of fire, accuracy, radius of effect and battlefield mobility.
Here's how the US Army's rankings fell.
Caption:Fox Van AllenPhoto:Sgt. Anthony Jones, 45th Infantry Brigade Combat Team
Dating back to 15th-century Spain, the arquebus is the earliest shoulder-fired gun used in warfare. It required the use of a fork rest for support.
The relatively inexpensive gun spread quickly across the world, but it was inaccurate at long range, took up to a minute to reload and could cause permanent hearing loss in its users.
The flintlock musket, first appearing in Europe during the early 17th century, was a major upgrade over the arquebus. It was much lighter, eliminating the need for a support.
The muzzle-loaded "Brown Bess" musket, seen here, a favorite of the British army in the 18th century, could fire four rounds a minute. Misfires proved a major problem, though, and it could not be used when wet.
Unlike front-loaded muskets, breech-loading rifle rounds are loaded into the rear of a barrel, saving time and increasing safety. Grooves bored into the gun's barrel -- rifling -- stabilized bullets during firing, improving accuracy.
This photo of an African American Buffalo Soldier holding a breech-loading rifle dates to the 1890s, though the weapons were used earlier, in the American Civil War.
Lethality Index: 229
Published:Caption:Fox Van AllenPhoto:Transcendental Graphics/Getty Images
Springfield model 1903 rifle
Popularly used by American troops in World War I, this rifle could be fired semi-automatically, thanks to its use of five-round magazines. It quickly gained a reputation as a reliable, accurate and deadly weapon.
Use of the gun as a sniper rifle continued throughout World War II, though its short range (600 yards) limited its use.
Developed by the British, tanks first appeared on the battlefield during World War I's Battle of Flers-Courcelette in September 1916. The heavily armored vehicles were designed to break through stalemates and cross trenches.
Tanks such as the Mark I, seen here, were incredibly slow and subject to frequent breakdowns. The poorly ventilated cockpits, meanwhile, would often fill with toxic gases.
World War I was the first major conflict to see planes put on the offensive.
Early bombers lacked proper sights and could only carry small loads of simple explosives. Two-seated fighters would typically have a front-mounted machine gun for offense and a rear-mounted one for defense.
Officially adopted by France in 1898, the 75mm field gun was designed to shower enemy forces with explosive shrapnel shells at a rate of 15 rounds per minute.
By 1916, these guns were firing toxic mustard gas and phosgene shells.
Lethality Index: 340,000
Published:Caption:Fox Van AllenPhoto:Thomas Samson/AFP/Getty Images
V-2 ballistic missile
Created by Germany during World War II as a weapon of revenge, the supersonic V-2 rocket was first used to bomb London in 1944. Over 3,000 V-2s were launched, killing 2,754 people in London alone and destroying enough buildings to cause a housing crisis. Thousands more concentration camp prisoners died in their construction.
Lethality Index: 861,000
Published:Caption:Fox Van AllenPhoto:Science & Society Picture Library
Automatic grenade launcher
The MK-19 automatic grenade launcher, seen here, was developed by the US during the Vietnam War. The belt-fed weapon fires 40mm grenades with an effective range of 1,600 yards.
Its grenade blasts likely kill anyone within 16 feet and wound those within 50 feet.
Lethality Index: 1,500,000
Published:Caption:Fox Van AllenPhoto:David K. Dismukes/US Army/Getty Images
World War II Tank (Sherman M4)
By the end of World War II, the US had built more than 40,000 M4 Sherman tanks, for its own use and to lend to Britain, France, Poland, China and Canada.
With a top speed of 30 mph on roads, it was much faster than tanks used in World War I.
The most powerful nuclear weapon ever used offensively was Fat Man, a roughly 20-kiloton plutonium device detonated over Nagasaki, Japan on August 9, 1945.
The blast, seen here from Koyagi-jima, killed up to 40,000 people immediately, with at least as many more deaths to come from the lingering effects of radiation.
Lethality Index: 48,550,000
Published:Caption:Fox Van AllenPhoto:Hiromichi Matsuda/Handout/Getty Images
25-megaton hydrogen bomb
The B-41 hydrogen bomb, first deployed in September 1960, is the most powerful weapon ever created by the US, with a maximum yield of 25 megatons, or equivalent to 25 million tons of TNT. With a lethality index roughly 4,000 times greater than Fat Man, it's also the most deadly.
Thankfully, the thermonuclear device was retired shortly after its creation. The US' current most powerful weapon is the B83 bomb, with a yield of "just" 1.2 megatons.