The emperors, who fear the mutterings of the guard-corps much more than they do those of the Senate, often shower special bonuses upon the Prætorians. Their centurions and still more their tribunes are welcome guests in the most aristocratic houses in Rome. Their weapons are the same as the legionaries’, but, of course, their armor is of the finest; and on gala occasions when the whole corps is ordered out with gilded or silvered helmets and cuirasses over purple military cloaks, the sight of these thousands of tall powerful warriors marching in perfect rhythm is astonishing beyond words. In one important respect the organization of the Prætorians differs from that of the regular legionaries: their nine cohorts number 1000 instead of 600 men each and the whole guard-corps therefore amounts to about 9000 men. Considering that these troops are chosen for their splendid physiques, and are trained for years in every military accomplishment, remarkable will be the foe of like numbers that can withstand them. As for the city of Rome, its whole raging populace is like mere chaff and straw if the trumpets sound through the camp, and the centurions thunder down their files, “Open the gates and clear the streets!” =267. The City Cohorts (_Cohortes Urbanæ_).=--The Prætorians, however, have some humbler comrades in Rome, in addition to police-firemen, the vigiles. Sometimes the guard-corps must follow the Emperor on campaign, but nevertheless the capital needs a fixed garrison. The City Præfect (see p. 300), therefore, commands four additional cohorts (_cohortes urbanæ_) also of 1000 each, in a special camp in the northern part of the metropolis. These “City Cohorts” are organized much like the Prætorians, and in a grave emergency would act with them; but they have longer terms of service, lesser pay, severer discipline. It is far less of an honor to belong to this force than to the Prætorians, and there is little “fraternizing” between its members and the haughty guard-corps. However, they make 4000 more armed men always available for the defense and control of the city. Added to these can, of course, be the vigiles (7000 strong), easily changeable into genuine soldiers in a crisis. This makes the total garrison of Rome, while the Prætorians are in the city, around 20,000 men, plus usually some marines detached from the squadrons at Ostia and Misenum. The frontiers are far away, but the central direction of the great imperial war machine is inevitably at Rome. From the Prætorian barracks issue those orders which can set the legions marching against the Caledonians of North Britain or the Arabs of the Syrian deserts. There can be no better place, therefore, for inquiry about the organization and discipline of that grim efficient engine which maintains the Pax Romana and makes possible the splendid, artificial Græco-Roman civilization.