On September 3, 1939 France declared war on Germany. That same month, Gnome et Rhône produced 500 engines. In 1940, it would make a total of 1,000 per month. Unfortunately, after being nationalized in 1937, the aircraft industry was unable to complete its reorganization and could not keep pace with the high production rates demanded by armed conflict.

Several aircraft capable of standing up to Germany's brand-new Messerschmitt BF109E were rushed into service: the Bloch 152 with a Gnome et Rhône 14N engine in 1939 and the Hispano-Suiza 12Y-powered Dewoitine 520 in 1940. Gnome et Rhône engines also powered the modern Bloch 174 twin-engine reconnaissance plane, of which only a few were built. This was the plane flown by Antoine de St. Exupéry on the missions described in his book "Flight to Arras".

There was also the very promising Arsenal VG 33, powered by Hispano-Suiza, but it would arrive on the scene too late for the battle of France.

1939 - 1944 : France loses its head start

From June 1940 to the middle of 1944, Gnome et Rhône and Hispano-Suiza, like all French companies, were obliged to work for the occupying forces. Gnome et Rhône continued production of its own engines and also participated in the manufacture of BMW engines. During the dark days of the Occupation, management stayed on the job to protect their employees and production facilities. Their subtle resistance was expressed in a sustained lack of productivity: the company produced about 8,500 engines during the 55 months of the Occupation, averaging slightly less than 150 engines a month - while the Germans were counting on 25,000! Other actions were made including sabotaged engines, the continuing of secret design studies and protection of workers requisitioned by the Obligatory Work Service in Germany.

In 1941, Gnome et Rhône took over SNCM, formerly Société des Moteurs et Automobiles Lorraine. As the end of the conflict neared, the company increasingly fell into a state of disrepair. And in May 1944, the large Gennevilliers plant, home to the Gnome and Rhône foundries in particular, was completely destroyed by U.S. bombers.

During the occupation, French industry fell considerably behind its competitors in allied countries. For example, the United States produced over 250,000 engines in 1944 alone. French engine makers would have to catch up with the gigantic head start taken by competitors in the United States (Pratt & Whitney, Wright, Allison), Britain (Rolls-Royce, Napier, Bristol) and Germany (Daimler-Benz, BMW and Junkers). At the same time, France was almost totally invisible in the up and coming field of jet propulsion.

Reconstruction and the founding of Snecma

After the war, the French aerospace industry had to be completely rebuilt: factories had been destroyed, programs were out of date, productivity was in free fall. Furthermore, Gnome et Rhône's industrial resources had been pared, since occupying forces had transferred a number of machines to Germany, and most plants had been damaged by allied bombing.

Production kicked off again with repair work on American Sherman tanks. But defense orders were way down, and the company diversified into the production of tractors, cream separators, autoclaves, machine guns and motorcycles.

Hispano-Suiza purchased licenses or teamed up with other manufacturers to produce the Nene, Tay and Tyne engines, powering aircraft such as the Mistral, Ouragan and Vampire.

In a drive to restructure the domestic aero-engine industry, the French government nationalized Gnome et Rhône on May 29, 1945, creating the "Société Nationale d'Etude et de Construction de Moteurs d'Aviation" - Snecma.

The new company would unite some of the leading engine manufacturers from the pioneering days of aviation, namely Gnome et Rhône, Renault and Lorraine. Snecma could arguably lay claim to being the oldest aircraft engine manufacturer in the world, but it also suffered from a considerable technology gap with its competitors. Right from the end of the war, Snecma focused on the development of jet engines. At the same time, it continued production of Hercules piston engines (licensed from the Bristol Aerospace Company), which would power the Noratlas transport until 1964. But very quickly the piston engine was outdated, and the industry would no longer talk in terms of "horsepower", but of "thrust".

Group O and the Atar family

From 1945 to 1964, Snecma would contribute to the recovery of the French aviation industry under the impetus of its chairman Henri Desbruères. In 1945 he created two new departments, flight testing and jet engines, which would handle repairs of Pratt & Whitney and de Havilland turbojets. Snecma's new jet engine department also worked on two turboprop engine models (TA 1,500 and 5,000 hp), along with Rateau, a French firm specialized in turbine propulsion. They were abandoned 10 years later.

Like their counterparts in the U.S., Britain and Soviet Union, the French government was very interested in German technological prowess, in particular a certain Dr. Oestrich, head of the turbojet division at BMW (Bayerische Motor Werke). He set up shop in a former Dornier plant on the shores of Lake Constance in Lindau-Rickenbach, along with his team of 120 engineers. This was the beginning of the famous Group O, whose greatest success would be the Atar jet engine [still in service today].

The Group O's Rickenbach aeronautics facility was made part of Voisin, a subsidiary of Snecma. Their task was to design a French jet engine, based on the BMW 003. In fact, it was the name of this facility that gave its name to the new engine: Atar (ATelier Aéronautique de Rickenbach). A new era had started for French military engines. On March 26, 1948, the Atar 101 V1 developed 1,700 kg of thrust during a ground test.

These jet engines would signal the revival of the French aircraft industry, as powerplants of Dassault's famous warplanes, from the Mystère, Super Mystère, Vautour and Etendard, to the Mirage III, IV and V. For the first time since the war, the country's planes would be powered by engines "Made in France".

On November 29, 1952 a Mystère II made its first flight under Atar 101D power. The Mirage IIIA started flight tests in 1958 and quickly reached Mach 2 in level flight - the first time this speed was reached in Europe. The Mirage IV bomber, powered by two Atar 9D engines, made its first flight in 1959. On September 19, 1960 it set a world closed circuit speed record, at 1,820 kph. The very successful partnership between Snecma and Dassault made the Mirage fighter a striking success on export markets.

While pursuing development of the Atar, Snecma also briefly became an aircraft manufacturer, as it worked on a vertical takeoff aircraft project from 1952 to 1959. The Atar C400 P2, dubbed "Atar volant", made its first demonstration flight in 1957, followed by the construction of the C450 Coléoptère, an experimental plane with an annular wing. But the C450 crashed in July 1959, putting an end to the program, although the pilot escaped badly hurt but alive.