Despite a suspension of the Mille Miglia by Mussolini due to the fatal accident in 1938 that resulted in the death of 10 spectators a smaller version of the event, officially called the Gran Premio di Brescia was held over a triangular course with Brescia, Mantua and Cremona at its apexes. The race entailed nine laps over the 104 mile circuit.
Enzo Ferrari having left Alfa Romeo was preparing cars of his own based upon engines and chassis of the 1100 Fiat. The Auto Avio Costruzioni 815 was the first Ferrari car that was fully designed and built by Enzo Ferrari. Bound by contracts after leaving Alfa Romeo, however, Ferrari was not allowed to call this car a Ferrari. Instead he set up shop under the name AAC (Auto Avio Costruzioni), and strictly speaking the car was named AAC tipo 815. It was named this because it had an eight cylinder, 1.5 L engine. Using the same facilities as his earlier Scuderia, Ferrari hired well-known technicians Luigi Bazzi and Federico Giberti, and engineers Vittorio Bellentani and Gioachino Colombo.
Ferrari then put in charge of the project Alberto Massimino, a talented 45-year-old engineer who had moved to Modena to work on the Alfa 158 racecar. Increasing border tensions throughout Europe were causing severe materials shortages, so Ferrari had his men use a Fiat 508 C as their starting point. Fiat had made a handful of these mainstream sedans into endurance racers, so Ferrari’s team reinforced the chassis but left untouched the brakes, transmission, steering, and front suspension. For the engine Ferrari took two 508 C 1100cc four-cylinder engines, reduced the bore and stroke, cast a new block and cylinder heads, and joined the two engines together. The result was an inline 1496cc 8-cylinder that produced 72 horsepower at 5500 rpm.The two 815s were to be driven by Lotario Rangoni and the son of Antonio Ascari, Alberto. One dominated its class and ran as high as 10th overall late in the race. Both had to retire with mechanical failures, causing Ferrari to note a bit harshly, “The experiment that started so brilliantly ended in failure, largely because the car had been built too hastily.”
Alfa Romeo entered a team of 4 2.5-litre roadsters and were thought to be prohibitive favorites some pre-race experts pointed to one of the five car German BMW team as potential winners. Headed by Huschke von Hanstein the cars were both light and fast. The 328 became world famous after a special low drag and light weight touring 'Superleggera' coupe finished fifth overall during the 1939 24 Hours of Le Mans, convincingly winning the two-litre class in the process. One of the BMW 328s entered in the Mille Miglia was a limousine-bodied car that was tailored for racing and given aerodynamic features courtesy of Professor Wunibald Kamm. Kamm is best known for his breakthroughs in reducing car turbulence at high speeds; the style of car bodywork based on his research has come to be known as the Kamm-effect, Kammback or Kamm-tail. It is a car design characterized by a long, tapering roof and an abrupt, cut-off tail.
Two Delages were entered but the French government there refused to allow any of their citizens to enter as drivers and the cars were handed to Italians Piero Taruffi and Gianfranco Comotti. Mechanical troubles forced both cars to retire. The lead Alfa driven by Farina was able to work its way up to 2nd but could reach no higher. The spectators who were there that day saw the German team finish first, third, fifth and sixth with von Hanstein taking the top laurels. This would be the last major race on the continent before it became fully engulfed in the war.