The famous AC model was introduced in 1916. With its chain drive rear axle, the AC model earned an unparalleled reputation for reliability and durability, and was called on to help accomplish nearly impossible military and civilian tasks. The AC model was manufactured continuously through 1939 -- a remarkable 24 years, and 40,299 were built. The AC is not only credited with giving Mack its famous Bulldog identity, but also with achieving a degree of success and international fame that has never been accomplished by any other motor truck in history.
Mack built a military armored car on an AB Chassis for the New York National Guard. During World War I, Mack delivered approximately 4,500 AC model trucks of 3-1/2, 5-1/2, and 7-1/2 ton capacity to the US government. During that same period, Mack delivered over 2,000 units to Great Britain. These trucks did an outstanding job under very difficult conditions.
The story goes that the British soldiers ("Tommies") would call out when facing a difficult truck problem, "Aye, send in the Mack Bulldogs!" The primary, and generally universal, story is that the British engineers testing AC's and the Tommys in France said that "the Mack AC's have the tenacity of a bulldog." At that time, the symbol of Great Britain was the bulldog, and this was high praise for the trucks. American "Doughboys" expressed the same opinion of the truck.
A new holding company, the International Motor Truck Corporation, is formed; it assumes the notes payable obligations of the International Motor Company and owns 98 percent of its stock. The International Motor Company, through its ownership of the Mack Brothers Motor Car Company, the Saurer Motor Company, and the Hewitt Motor Company, becomes the operating organization, with its main plants in Allentown, PA (Mack), Plainfield, NJ (Saurer), and Brooklyn, NY (Hewitt).
The International Motor Company also owns the International Mack Motor Corporation, which had been set up in December 1915 to run most of the company-owned branches. However, by the end of World War I, the title of this company is changed to the Mack-International Motor Truck Corporation.