than any other problem that they have. If they desire that their
ships shall be free to sail the seas, and their citizens to carry
on business and to travel in other lands; and if they desire that
their merchants shall be able to export their wares and their farmers
their grain, also that the people shall be able to import the things
they wish from foreign countries, then they must be able to exert
actual physical force on the ocean at any point where vessels carrying
their exports and imports may be threatened. Naval ships are the
only means for doing this.

The possibility that an armed force sent to a given point at sea
might have to fight an enemy force, brought about first the sending of
more than one vessel, and later--as the mechanic arts progressed--the
increasing of the size of individual vessels, and later still the
development of novel types.

There are two main reasons for building a small number of large
ships rather than a large number of small ships. The first reason
is that large ships are much more steady, reliable, safe, and fast
than small ships. The second reason is that, when designed for
any given speed, the large ships have more space available for
whatever is to be carried; one 15-knot ship of 20,000 tons normal
displacement, for instance, has about one and a half times as much
space available for cargo, guns, and what-not, as four 15-knot
ships of 5,000 tons each. These two reasons apply to merchant ships
as well as naval ships. A third reason applies to naval vessels
only, and is that a few large ships can be handled much better
together than a large number of small ships, and embody that
"concentration of force" which it is the endeavor of strategy and
tactics to secure. A fourth reason is the obvious one that large