Technological change had an enormous effect on strategy, but little effect on leadership. The use of telegraph and later radio, along with improved transport, enabled the rapid movement of large numbers of men. One of Germany's key enablers in mobile warfare was the use of radios, where these were put into every tank. However, the number of men that one officer could effectively control had, if anything, declined. The increases in the size of the armies led to an increase in the number of officers. Although the officer ranks in the US Army did swell, in the German army the ratio of officers to total men remained steady.