The heavy tank existed as a category of armored warfare from the closing days of World War 1 (1914-1918) to the end days of World War 2 (1939-1945). At that time, it was superseded by the modern Main Battle Tank (MBT) which took the reins as the preeminent battlefield spearhead. Just beyond the scope of the heavy tank lay another, more specialized, categorization of tank that encapsulated dimensionally larger and heavier armored vehicles fielding considerable firepower. These came to be known as "Super Heavy Tanks" and were symbolized by several ventures from competing world powers.
Several nations took to design of such vehicles throughout the 1920s and into the 1930s while others evolved at frenetic, and sometimes desperate, paces during World War 2 proper. The tanks were typically over 80 tons (short) in weight and were very well armored, promoting stout sizes and carrying heavy weaponry of the day. Such qualities, however, came at a price for many proved ponderous movers, expensive to produce in the numbers required and complicated to operate in the scope of military wartime service. As such, many of these programs would fall to history or never advance beyond "paper" stages or wooden mockups. Others came to be "one-off" prototypes that were never ordered for serial production.
The French FCM F1 (FCM = " Forges et Chantiers de la Mediterranee") was a super heavy tank class vehicle that entered development just prior to World War 2 when signs of conflict became increasingly apparent across Western Europe. The design was put to paper and became a 150 tons (short) vehicle with a proposed length of 10.5 meters, a width of 3.1 meters and a height of 4.2 meters. Armor protection measured 100mm in thickness, able to withstand any anti-tank weapon of the time. Power was served through 2 x Renault KGM V12 engines of 550 horsepower each, delivering upwards of 1,100 horsepower combined. The hull was suspended atop a vertical coil suspension system for some cross-country capability. The powerpack drove a wheel-and-track arrangement which included a bevy of small road wheels to a hull side.
Beyond its stout armor, the FCM F1 carried the other super heavy quality: heavy weaponry. This was led by a 90mm DCA main gun housed in a primary turret set over the rear of the hull. The weapon was supplement by another individual turret set over the front of the vehicle and holding a 47mm SA37 series anti-tank gun. The multi-turret approach was, more or less, a vestige of a period gone by. The vehicle was to defensed by no fewer than 6 x machine guns to prevent infantry from assailing the vehicle. The machine guns would have covered all possible approaches to the tank.
In practice, the FCM F1 was not a "combat" tank by its true battlefield role for it was not intended as a direct counter to enemy armor. Instead it was seen as a breaching vehicle that could pummel fortifications at range and break through concrete, steel and earthen defenses set by the enemy. Direct tank combat would have been handled by supporting medium- and light-class tanks of the French Army. A breaching vehicle would be responsible for opening points in the enemy's defenses, allowing more nimble units to pass through and assail the defenders.
Before World War 2 had come to France, Germany added to its defensive-minded line of fortifications that made up the famous "Hindenburg Line". The new section came to be known as the "Siegfried Line". The line stretched from the Dutch border in the northwest to the Swiss border in the southeast and measured some 390 miles of concrete with steel structures manned by artillery and machine gun positions. The original line was begun in 1916 during World War 1 and faced the similar line of French forts making up the "Maginot Line" which was constructed from 1930 to 1940. Construction of the newer German section occurred from 1938 into 1940 under Adolph Hitler's order.
However, by this time in tank history, the FCM F1 approach showcased many tactical limitations. The multiple turret approach was quickly falling by the wayside for coordination of multiple gun positions by a single vehicle proved ineffective on the whole. Super heavy tanks were just that, heavy, and this limited their pace in keeping up with the main armored force. It also served to limit traversal over the old bridges dotting the European countryside and restricted faster transport by the European rail system. Despite its pairing of two engines, the FCM F1 would have held an estimated road speed of just 12.5 miles per hour. All these qualities made her more akin to the lozenge-shaped "steel beasts" of World War 1 appearing some decades prior than any modern, advanced combat system required of a more mobile, fluid war front.
In May of 1940, the German Army (with Italian elements) had advanced beyond France's neighbors and entered France proper with the purpose of securing its shipyards to the north and east and capturing the capital city of Paris. The invasion culminated with the Fall of France and the French surrender which placed such a stain on French military prowess for the decades that followed. The Fall of France ended any further development on any French-originated weapons including the FCM F1 - which by this time existed in only a single wooden mockup form and never advanced. The Battle of France lasted until June 22nd, 1940 and ended with a decisive Axis victory. Allied casualties numbers 2.26 million with 1.9 million captured.