pe which
cannot be invaded except across the sea, and secondly, because Britain
for that very reason has often been subjected to attempts at invasion
and has always frustrated them by denying to her adversary that
sufficiency of sea control which, if history is any guide, is essential
to successful invasion. But first I will examine two cases which might
at first sight seem to militate against the principles I have
enunciated. The brilliant campaign of Caesar which ended in the overthrow
of Pompey and his cause at Pharsalus, was opened by Caesar's desperate
venture of carrying his army across the Adriatic to the coast of Epirus,
although Pompey's fleet was in full command of the waters traversed.
This is one of those exceptions which may be said to prove the rule.
Caesar had no alternative. Pompey was in Illyria, and if Caesar could not
overthrow Pompey on that side of the Adriatic it was certain that Pompey
would overthrow Caesar on the other side. For this reason, and perhaps
for this reason alone, Caesar was compelled to undertake a venture which
he must have known to be desperate. How desperate it was is shown by the
fact that, not having transports enough to carry more than half his army
at once, he had to send his transports back as soon as he had landed,
and they were all destroyed on their way back to Brundusium. Antony his
lieutenant did, indeed, succeed after a time in getting the remainder of
his army across, but not before Caesar had been reduced to the utmost
straits. The whole enterprise moreover was not, strictly speaking, an
invasion of hostile territory. The inhabitants of the territory occupied
by both combatants were neutral as between them, and were willing to
furnish Caesar with such scanty supplies as they had. Again, an army in
those days needed no ammunition except the sword which each soldier
carried on his person, and that kind of ammunition was not expended in
fighting. Hence Caesar had no occasion to concern himself with the
security of his communications across the sea--a consideration which
weighs with overwhelming force on the commander of a modern oversea
expedition. "A modern army," as the late Lord Wolseley said, "is such a
complicated organism that any interruption in the line of communications
tends to break up and destroy its very life." An army marches on its
belly. If it cannot be fed it cannot fight. After the Battle of Talavera
Wellington was so paralysed by the failure of the Span