0 STUDENTS of war, the physical conditions likely to govern an armed conflict in the Pacific present a fascinating field for exploration. At the outset we are confronted by an arena so vast as almost to defy conception. In the case of an AmericanJapanese struggle, the war zone would extend north to south from the Bering Sea to the Equator and east to west from Panama to the Yellow Sea. Intermediate bases are few and far between. On the direct route from Honolulu to Tokyo, some 3,400 miles, there is not a single United States base capable of supplying the simplest needs of a battle fleet. It at once becomes evident, therefore, that the cruising endurance of ships must be a decisive factor in Pacific strategy. Compared with the old-time sailing vessel, the mobility of the modern steam-driven man-of-war is exceedingly limited. A battleship steaming at its most economical speed (9 knots) has a radius of only i5,000 miles; the corresponding figure for a cruiser of the io,ooo-ton class is i8,ooo miles, and for a destroyer 5,000 miles. These data apply to typical American ships, in all of which the cruising radius is superior to that of foreign vessels. It need hardly be said, however, that ships dare not proceed at very low speed in waters where enemy submarines are likely to be encountered. The menace of underwater attack would keep them moving at a relatively fast pace, and it therefore follows that a ship's maximum range at economical speed is no real guide to its operating radius