TheSwedish Stridsvagn 103 (or "S-Tank") was one of the most unusual tanks ever built. Designed to give good defensive firepower to enforce Sweden's armed neutrality, it's unique design came at a cost: it is absolutely no good on offense.  

During the Cold War Sweden maintained a position of armed neutrality. Sandwiched between NATO powers and members of the Warsaw Pact, it took neither side and prepared to defend its territory from all comers. The trick with armed neutrality is to appear strong enough to deter an enemy from attacking, while appearing weak enough to not look threatening. In other words, build a force that's weak in offensive firepower, but strong in defensive firepower. 

Tanks are inherently attack-oriented weapons, designed to wrestle territory away from the enemy. The solution, as the video above describes, was the S-Tank. A tank without a turret, it was designed to lay in wait and ambush invading enemy armor. It mounted the BritishL-7 tank gun, the same gun that equipped into early versions of the U.S. Abrams tank. 

Instead of sitting in a turret the gun was built into the hull, lowering the S-Tank's overall profile. The gun was aimed by moving the entire tank, horizontally by pivoting the tank using its tracks, vertically by raising and lowering the tank via its hydropneumatic suspension system. 

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This also made the tank remarkably small—current versions of the Abrams weigh nearly 70 tons, while the S-Tank weighed a mere 40 tons. But the S-Tank was still plenty tough. The S-Tank was even designed to survive a 5 kiloton tactical nuclear explosion. 

A defensive tank, the S-Tank needed to be as mobile as possible. A raised screen could be erected around the entire tank to make it float,  while its tracks would propel it through the water.

At some point in a war, Sweden might be compelled to take back territory from the enemy. Well, the S-Tank wasn't so great in this department. Because the gun was aimed by moving the entire tank, it was impossible to fire the gun accurately while the tank was moving. During an attack, the S-Tank needed to come to a complete stop to position itself to aim—and then it was very vulnerable. 

The S-Tank certainly wasn't a good fit for most countries. Eventually, it wasn't even for Sweden—in the 1990s, the country retired its S-Tanks and bought the excellent German-madeLeopard 2 tank. Never tested in battle, the S-Tank remains one of the most innovative—and weird—tank designs of all time.

Kyle Mizokami

Kyle Mizokami is a writer on defense and security issues and has been atPopular Mechanics since 2015. If it involves explosions or projectiles, he's generally in favor of it. Kyle’s articles have appeared atThe Daily Beast, U.S. Naval Institute News, The Diplomat, Foreign Policy, Combat Aircraft Monthly, VICE News, and others. He lives in San Francisco.