US Military
According to the Wikipedia, The US military is the next-largest in the world. It consists of various component branches such as US Army, US Marine Corps, US Navy, US Air Force, US Coast Guard and US National Guard. These departments are all portion of the United States Uniformed services and are controlled by the current president that acts as their Commander-in-Chief.
The quantity of US Air Force leads the US Military with over 37% of its total personnel. Taking the second and third spots are the US Navy with 24% and US Air Force with 23%. Lastly, Marine Corps and Coast Guards complete the list with 13% and 3% of personnel respectively.