ere undertaken--campaigns which ended and
were always intended to end, should the fortune of war so decree, in the
invasion of France and the overthrow of Napoleon. This opens up the
whole question of invasion, which will be discussed in the next
chapter.

CHAPTER VI

INVASION

England has not been invaded since A.D. 1066, when, the country having
no fleet in being, William the Conqueror effected a landing and
subjugated the kingdom. During the eight centuries and more that have
since elapsed, every country in Europe has been invaded and its capital
occupied, in many cases more than once. It is by no means for lack of
attempts to invade her that England has been spared the calamity of
invasion for more than eight hundred years. It is not because she has
had at all times--it may indeed be doubted if she has had at any
time--organized military force sufficient to repel an invader, if he
could not be stopped at sea. It is because she can only be invaded
across the sea, and because whenever the attempt has been made she has
always had naval force sufficient to bring the enterprise to nought. It
is merely a truism to say that the invasion of hostile territory across
the sea is a much more difficult and hazardous enterprise than the
crossing of a land frontier by organized military force. But it is no
truism to say that the reason why it is so much more difficult and more
hazardous is that there is no real parallel between the two cases. I
assume a vigorous defensive on the part of the adversary assailed in
both cases--a defensive which, though commonly so called, is really
offensive in its nature. The essential difference lies in this, that two
countries which are separated by the sea have no common frontier. Each
has its own frontier at the limit of its territorial waters, but between
these two there lies a region common to both and from which neither can
be excluded except by the superior naval force of the other.

For the moment an expeditionary force emerges from its own territorial
waters--which may be any distance from a few miles up to many thousands
of miles from the territorial waters of the adversary to be assailed--it
must be prepared to defend itself, and naval force alone can afford it
an adequate measure of defence. Military forces embarked in transports
are defenceless and practically unarmed. They cannot defend themselves
with their own arms, nor can the transports which carry them be so armed
as