2025-01-25T10:23:02Z Read in app An illustration of the hybrid tank prototype. Landships.info This story is available exclusively to Business Insider subscribers. Become an Insider and start reading now.Have an account? The US military sought to develop a tank to break the trench warfare stalemate during World War I.British and French tanks inspired the US Army to design their own armored vehicle.The US tractor-turned-tank failed but influenced future tank and armored vehicle development.The US military sought an armored weapon to bypass the heavily defended trenches along the Western Front during World War I.Traditional infantry and cavalry tactics weren't cutting it against the heavy artillery and especially machine guns, calling for shielded firepower to strike fortified positions. The emergence of British and French tanks prompted the US Army, which lacked experience with tank development, to design a tank of their own to overcome the stalemate.But the US' ambitious endeavor to create a successful armored vehicle fell short, with a prototype that was impractical for combat just as the war was ending.Nonetheless, the failed prototype laid the groundwork for tanks and armored vehicles of the future. Tractor turned tankA 1917 Holt gun tractor on display at a fair in Dorset, England. Matt Cardy/Getty Images Leveraging its domestic transportation industry, the US military partnered with Holt Manufacturing Company, known for its tractors used to tow artillery.They developed a prototype built off of an existing Holt Model 75 tractor powered by a modified hybrid gas-electric engine. The four-cylinder gasoline engine supplied power to two General Electric motors that drove each track individually for improved mobility and had enough space at the front to accommodate its main cannon.Tracked treads better distribute weight than wheels and allow a vehicle to cross more types of terrain an especially important quality for heavy vehicles whose weight is measured in many tons.DesignSketches that detail the design of the Holt hybrid tank prototype. miSci- Museum of Innovation & Science/Google Arts and Culture Protected by a layer of 15mm steel armor, the tank could accommodate a crew of six commander, driver, two machine gunners, a main gunner, and a loader.It was armed with a Vickers mountain cannon at the front and two machine guns on either side of the boxy tank.The tank was a response to the annihilating firepower seen on the Western Front, where artillery barrages were commonplace and advancing columns of foot soldiers were mowed down by emplaced machine gunners.The sheer scale of the carnage was shocking. In the Allied offensive known as the Battle of the Somme in 1916, an estimated 620,000 British and French troops were killed or wounded.A shielded hull was intended to carry troops past deadly machine gun nests and target those positions with heavy fire, clearing the path for infantry.ProblemsThe tank prototype rolls over a hill. Landships.info However, its bulky armor and equipped weaponry made the prototype of the hybrid tank far too heavy, weighing about 25 tons. Its 90-horsepower engine struggled to propel the tank, which moved at a top speed of 6 mph and was practically immobile on an incline.That was hugely underpowered. A modern M1 Abrams, the US Army's main battle tank, moves its 68-ton bulk around with a 1,500-horsepower engine.A more successful variationPeople ride atop two tracked vehicles, one of which has an electrically propelled gun mount. miSci- Museum of Innovation & Science But the US military didn't give up. Instead, it chose to create a variation of the first design by adding just an electrically propelled gun mount to the gas-electric tractor.While more successful than its predecessor, the armed tractor ultimately never made it to combat since it was completed after the armistice was signed and WWI came to an end.Poor timingA person riding the hybrid tank shows their head above the vehicle. miSci- Museum of Innovation & Science Though the hybrid tank didn't appear on the battlefield, it did appear on the silver screen.American animation studio International Film Service, owned by media magnate William Randolph Hearst, produced a miniseries in 1917 that featured vehicles similar in design to the Holt tank.The series' final battle featured US troops ahead of a twin-turreted prop tank, though much of the footage for the series has been destroyed or lost in the last century.