In the early 1980s, the Brazilian concern of Engesa undertook a private venture initiative to produce a modern Main Battle Tank (MBT) firstly for the budget-minded foreign market and, secondly, to the interested Brazilian Army. For decades, the Brazilian Army had relied on foreign procurement ventures that largely resulted in outgoing American tank stocks. The Engesa concern was founded in 1963 with the primary focus of military vehicles and ended producing a long line of light armored platforms, utility vehicles and military-grade trucks. While eventually defunct in 1993, Engesa set its hopes on the design, development and ultimate production of an indigenous MBT system in the years prior.
Design of the new MBT began in 1982 and proceeded into 1986 under the designation of EE-T1 "Osorio". It became a conventional combat design by modern Western standards featuring an operational weight of 43 tons, a four-man crew and a 120mm smoothbore main gun. Dimensionally the EE-T1 sported a running legnth of 10 meters with a width of 3.26 meters and height of 2.37 meters. The crew consisted of the driver (in the front hull) and the commander, loader and gunner (residing in the turret). Armor was developed from an aluminum/steel/carbon/ceramic formula intended to protect the vital internals of the machine against the threats of the then-modern battlefield. Power was supplied through a 12-cylinder diesel-fueled engine of 1,100 horsepower output for a top road speed of 43 miles per hour and an operational range of 340 miles. The suspension system was designed around a hydropneumatic arrangement tied to the six double-tired road wheels to improve cross-country travel. The drive sprocket was at the rear of the track system with the track idler at the front. Side skirt armor protected the critical upper portions of the tracks. Overall a fine design by modern standards.
Primary armament of the prototype was the British-born 105mm L/52 L7 rifled main gun. As was common practice (and still remains so), a 12.7mm Browning M2HB heavy machine gun was fitted atop the turret roof to counter the threat posed by low-flying attack aircraft (such as helicopters) and light armored vehicles. While not utilizing a 7.62mm coaxial machine gun mounting, the EE-T1 instead fielded a second 12.7mm heavy machine gun in the coaxial position. 12 x smoke grenade dischargers were installed along the turret sides (rear) in two banks of six.
The EE-T1 emerged as an initial prototype form in 1985. The Saudi Army proved the only true interested party at the time and successfully trialed the Brazilian system against power-players in the American M1 Abrams and British Challenger 1 (the ultimately abandoned French AMX-40 was also in contention). The EE-T1 proved to be a capable machine with the required firepower, performance and survival features sought in a wholly modern design - also at the desired cost. However, the Saudi relationship with the United States - and the invasion of nearby Kuwait by Iraq (1990) - prompted the Saudi government to continue its standing relationship with the Americans and, thusly, the M1 Abrams was selected as the official MBT of the Saudi Army. This maneuvering proved a defining blow to the EE-T1 program and, although a second prototype had been completed (this with the French GIAT 120mm smoothbore main gun), the project ultimately fell out favor. As the M1 Abrams gave an excellent account of itself on the world stage in the Persian Gulf War (1991), the Engesa concern went on to bankruptcy in 1993. The two prototypes were handed over to the Brazilian Army for further consideration though the tank was, now and forever, destined never to see the light of serial production.
The Brazilian Army is today made up of 378 ex-Belgian/ex-German Leopard 1 MBTs (1A1 and 1A5 versions, 128 and 250 respectively) with 91 ex-American M60 Patton MBTs. The M60s are being retired as of this writing (2012) as the Brazilian Army attempts to modernize its inventory.