For several years, the Automobile Club de France (ACF) had been trying to reduce engine sizes in racing which it saw as increasingly dangerous with their higher speeds.

This year, for the first time, it mandated a maximum engine size of 4.5-litres[3][4] along with an allowable weight range of 800–1,100 kg (1,764–2,425 lb) (excluding fluids and tools).

It returned on a long, undulating 12 km (7.5 mi) straight before coming to a steep downhill right-left switchback (nicknamed le piege de la mort – the Death trap) and a hairpin at Les Sept Chemins to complete the lap.

[7][8][9] At the end of June the two hairpin turns were concreted and the course was re-laid with granite chips to prevent its break-up and coated with calcium chloride to reduce the dust raised.

A week later, the French Grand Prix was held under an increasingly tense political situation across Europe.

They arrived with the new EX-5 (or ‘L-45’, after its engine size) for team drivers Georges Boillot, Jules Goux and Victor Rigal.

[10] New French company Alva convinced Ferenc Szisz, winner of the inaugural Grand Prix in 1906, out of retirement to lead their team.

The most serious opposition to the French teams would come from Mercedes, returning to the Grand Prix for the first time since winning in 1908.

Alongside him were Otto Salzer, young Mercedes director Max Sailer,[13] French veteran Louis Wagner and Belgian Mercedes-agent Théodore Pilette.

The new Opel was a development of the 4.0-litre 1913 model, retaining its single-overhead camshaft, with four valves per cylinder and a live rear axle like the Mercedes.

Great Britain was represented by Sunbeam (Resta, Lee Guinness and Chassagne) and Vauxhall who included American Ralph DePalma in their squad.

The extended tail was cut off to save weight and, from the long straights and winding corners, the engineers recommended changing to a five-speed gearbox.

[9] During practice though the Peugeot drivers found their cars handled badly, with the poor weight distribution having the spare tyres stowed in the tail.

[9] Whether it was racing inexperience, or internal rivalry with team-leader Lautenschlager to prove a point, Sailer had pushed his car too hard and stopped with a broken conrod along the Gier River on the sixth lap.

Lautenschlager was running out of brakes and his stop became a bit of a shambles as the normally well-drilled Mercedes team cost him 2–3 minutes in the pits.

[9] But the Peugeot Dunlops were wearing far quicker – Boillot had to make six pitstops for tyre changes to the single ones for the Mercedes cars.

His arm broken, it fell to his less injured mechanic to slowly get the car back to the pits where Szisz could get attention.

[18][9] So after seven hours of racing, Mercedes took a crushing 1-2-3 victory with Lautenschlager repeating his 1908 win ahead of Wagner and Salzer.

[11] The French crowd was silent, with Goux's fourth place nearly ten minutes back ahead of Resta's Sunbeam being scant consolation.

[11][10] Georges Boillot was initially the personal driver for Marshal Joffre,[20] but then transferred to the French Air Force (Armée de l'Air) as a fighter pilot.