Stealth, or the idea of reducing the ability of the enemy to detect a weapon, has been around since the first caveman sewed a pocket into his clothing and hid a rock in it.

Thousands of years later, with the ability to detect objects on the ground, in the air and at sea using electromagnetic radiation, hiding weapons in plain sight has become much harder. The idea of making an aircraft invisible to radar waves was not pursued as the properties of radar with regards to object shape were not fully understood.

Recommended: US Army's 5 Most Lethal Weapons of War

Pyotr Ufimtsev, a Russian physicist, published a number of papers on predicting the reflection of electromagnetic waves—radar waves. The Soviet Union, not understanding the gravity of his work, translated many of them into English.

But aerospace engineers at Lockheed did, and extrapolated from it a correct theory on reducing the radar cross section of aircraft. The result was the Lockheed F-117A Nighthawk stealth “fighter.” Since then, stealth has been an integral part of every tactical aircraft deployed by the United States. Here are five of the most lethal stealth weapons of war.

Recommended: Russia's Armata Tank vs. America's M-1 Abrams - Who Wins?

SR-71 Blackbird:

Famous for being the fastest plane ever built, the SR-71 is less well known for being a stealthy aircraft. The SR-71, which cruised at Mach 3.2, was one of the first aircraft to incorporate multiple stealth features into its design.

Recommended: Who Swallows North Korea after it Collapses? 

First flown in 1962, the SR-71 incorporated four stealthy features into its design. First, surfaces were designed to avoid reflecting radar waves. Second, the aircraft’s wings, tail and fuselage made use of composites, alternating with titanium, on the idea that composites were radar-absorbing. Third, the massive J-58 afterburning engines, with their large air-gulping inlets were positioned close to the fuselage of the airplane.

The fourth feature incorporated into the SR-71 was a black paint infused with tiny iron ferrite spheres. The paint, which gave the SR-71 its distinctive “blackbird” look and helped reduced the plane’s radar cross section, cost $400 a gallon. Altogether, the SR-71’s stealthy design gave it a radar cross section of less than 10 square meters. By comparison, the radar cross section of an early F-15 Eagle is 100 square meters.

F-117 Nighthawk:

The first operational stealth aircraft, the F-117 is often mistakenly referred to as a “stealth fighter.” Contrary to popular belief, the F-117 is actually a tactical bomber, with no air to air capability.

The F-117 was developed from the top secret Have Blue project, which produced two stealth technology demonstrating aircraft. The Have Blue aircraft emphasized a low radar signature over aerodynamic performance, and indeed needed fly-by-wire technology just developed for the F-16 to prevent the aircraft from losing control in flight. Fifty nine F-117 Nighthawk stealth fighters were eventually built.

The existence of the “stealth fighter” was speculated for much of the 1980s, reaching a frenzy after a July 1986 crash of a F-117 outside Bakersfield, California. The attempted cover-up only served to heighten public interest, and the Air Force confirmed the existence of the plane in 1988.

The F-117 first flew in combat in 1989, when it bombed targets during the invasion of Panama. The F-117 next flew in Operation Desert Storm, flying nighttime missions over Baghdad, and participated in no-fly zone operations against Iraq in the 1990s. F-117s flew missions over Kosovo in 1999, and Iraq during 2003’s Operation Iraqi Freedom. The F-117 was retired in 2008.

B-2 Spirit:

First revealed in 1988 by the Northrop Corporation, the B-2 Spirit was to be America’s first truly stealthy strategic bomber. The tailless design was meant to minimize the aircraft’s radar signature, allowing it to penetrate Soviet air defenses during a nuclear war.

The end of the Cold War ended justification for a full scale order of 132 planes, and only 21 were built. The success of the F-117 Nighthawk during the 1991 Gulf War showed the utility of stealthy aircraft capable of conventional precision strike, and the B-2 fleet was modified to conduct conventional missions. The B-2 is capable of carrying everything from B61 nuclear gravity bombs to conventional Joint Directed Attack Munition (JDAM) bombs, to the enormous, 30,000 pound Massive Ordnance Penetrator (MOP).

The B-2 first flew in combat over Kosovo in 1999. The aircraft has also flown in support of Operation Enduring Freedom and Operation Iraqi Freedom. In 2011, three B-2s flying from the continental United States struck a Libyan airfield during Operation Odyssey Dawn.

F-22 Raptor:

The first operational stealth fighter, the F-22 Raptor was designed to replace the F-15 Eagle. Unlike previous American stealth aircraft, including the F-117 and B-2, the F-22 was to be a fighter, using stealth to give it decisive advantage in air-to-air combat. Declared operational in December 2005, the F-22 is the world’s best fighter, outclassing all current and projected fighters, and the only operational so-called fifth generation fighter.

The F-22 began life in the late 1980s as the Advanced Tactical Fighter (ATF). ATF would be the first aircraft to incorporate stealth in a highly maneuverable, fighter-type platform. The F-22 is designed to provide minimal radar and infrared signatures, the two primary homing mechanisms for air-to-air missiles. The radar cross section of the F-22 is estimated by manufacturer Lockheed Martin as, from some angles, approximate to a “steel marble.”

The U.S. Air Force originally planned to order 750 F-22s to replace the F-15A and F-15C, but orders were slashed to 183 aircraft.

Ohio-class nuclear missile submarine:

Stealth doesn’t just apply to aircraft—submarines have been incorporating stealthy features for decades. Among submarines, the most powerful combination of lethality and stealth is almost certainly the Ohio-class nuclear powered ballistic missile submarines.

A popular—possibly apocryphal—legend about the Ohio class holds that they were never detected by rival Soviet submarines and submarine detection systems.

The Ohio submarines, at 18,450 tons submerged are the largest submarines ever built by the United States. Stealthy features include a cylindrical, fish-shaped hull for fast movement with minimal noise. Noise-generating equipment is placed on sound-isolating mounts. The nuclear missile silos, laid out in two rows behind the sail, are flush with the hull to decrease flow noise. The subs also mount two steam turbines, one for quiet operation.

Eighteen Ohio-class submarines were built—fourteen serve on as ballistic missile submarines while four were rearmed with conventional Tomahawk cruise missiles.

Kyle Mizokami is a writer based in San Francisco who has appeared in The Diplomat, Foreign Policy, War is Boring and The Daily Beast. In 2009 he co-founded the defense and security blog Japan Security Watch.

This first appeared back in 2015.

Image: Reuters.