After serving as statistician and then as vice-president for the UMWA, Lewis became that union's acting president in 1919. On November 1, 1919, he called the first major coal union strike, and 400,000 miners walked off their jobs. President Woodrow Wilson obtained an injunction, which Lewis obeyed, telling the rank and file, "We cannot fight the Government." In 1920, Lewis was elected president of the UMWA. He quickly asserted himself as a dominant figure in what was then the largest and most influential trade union in the country.