These colours, first the pendant, then from 1634 to 1864 the pendant and jack, and finally all three of them together, have served to distinguish ships "of war" from ships not fitted out for war, but the pendant and ensign, with occasional assistance from a masthead flag, have also served for a secondary distinction within the main category "of war," namely, that tactical distinction of lesser groups among a collected body of ships of war which may be termed squadronal distinction. Squadronal distinction colours were the outcome of the development of naval tactics. So long as a battle between two opposing fleets of any size is to be fought pell mell, like a gigantic football scrimmage, there is obviously no need for other flags than such as mark out the two opposing parties, with perhaps the addition of special flags of command to denote the ships of the two leaders. But directly the attempt is made to bring intelligence to bear as well as courage and brute force, to derive advantage from superior skill in manoeuvring, and to use the ship itself as an actual weapon instead of a mere transport to carry opposing warriors into touch with each other, it becomes necessary to co-ordinate the movements of the various ships under the direction of some master mind. If these ships are few in number their movements can be readily directed from one centre; but if they are many, experience shows that the whole fleet must be divided into distinct parts (called squadrons) of which the principal one will remain under the direct control of the commander of the whole fleet, while each of the others is placed under the immediate control of a subordinate commander, who is directly in touch with the Commander-in-Chief and acquainted with his intentions and wishes. It then becomes necessary to furnish the ships comprising the various squadrons with some means whereby they may be readily distinguished should they become separated, or should the fleet fall into temporary disorder. Among the ancient Egyptians, Greeks, and Romans this appears occasionally to have been provided for by painting some part of the ship in a distinctive colour[297], but this method has the disadvantage that the ships of the various squadrons are not readily interchangeable, and it appears to have gone out of use before the Christian era. With the passing of the great days of the Greek states the art of sea warfare suffered an eclipse from which it did not recover for many centuries, and we meet with no further indication of the existence of fleets organised in squadrons until the thirteenth century of our era. The proper stimulus for the development of the art of fleet tactics can only be supplied by the collision of two maritime powers of fairly equal intelligence and resources. This condition was first supplied by the rivalry of Genoa, Pisa, and Venice for the sea-borne trade of the Mediterranean.