From these changes in the methods of war on land it may be safely inferred that a nation which would be strong in war on land must be strong in all sorts of manufacturing, and particularly in the metallurgical industries. A nation chiefly devoted to agriculture and the ancient trades cannot succeed in modern war, unless it can beg, borrow, or buy from sympathizers or allies the necessary artillery and munitions. No amount of courage and devotion in troops can make up for an inadequate supply of artillery, machine guns, shells, and shrapnel, or for the lack of ample means of rapid transportation. Only in a rough country without good roads, like the United States in 1861-65, or Serbia or Russia now, can the rifle, light artillery, and horse or ox wagons win any considerable success; and in such a country the trench method can bring about a stalemate, if the combatants are well matched in strength, diligence, and courage. The changes in naval warfare are almost equally remarkable. Mines and submarines can make the offensive operation of dreadnoughts and cruisers near ports practically impossible, and can inflict great damage on an enemy's commerce. Hence important modifications in the rules concerning effective blockade. In squadron actions victory will probably go to the side which has the gun of longest range well-manned. Defeated war vessels sink as a rule with almost all on board. Commercial vessels can seldom be taken into port as prizes, and must therefore be sunk to make their capture effective. There have been no actions between large fleets; but the indications are that a defeated fleet would be sunk for the most part, the only vessels to escape being some of the speedier sort. Crews would go down with their vessels. Shore batteries of long-range guns can keep at a distance a considerable fleet, and can sink vessels that come too near. Mines and shore batteries together can prevent the passage of war vessels through straits ten to fifteen miles wide, no matter how powerful the vessel's batteries may be. Every war vessel is now filled with machinery of various sorts, much of which is delicate or easily disabled. Hence a single shell exploding violently in a sensitive spot may render a large ship unmanageable, and therefore an easy victim. A crippled ship will probably be sunk, unless a port is near. To build and keep in perfect condition a modern fleet requires dockyards and machine shops of large capacity, and great metallurgical industries always in operation within the country which maintains the fleet. No small nation can create a powerful fleet; and no nation which lives chiefly by agriculture can maintain one. A great naval power must be a mining, manufacturing, and commercial power, with a sound banking system available all over the world.