 The first such unit was based in Rome and were known as the Praetorian Guard, and a second similar formation were known as the Cohortes urbanae.The legions, which had been a mix of life professionals and civilian campaigners, was altered into a standing army of professionals only.The actual structure of the cohort army remained much the same as in the late Republic, although around the 1st century AD the first cohort of each legion was increased in size to a total of 800 soldiers.