st have been the hills
to the south of Canterbury, nearly a day's march from the sea.

If Caesar landed, as we know from Dion Cassius that he did, in the
same place as he had done in the previous year, he must have known all
there was to know about the natural facilities there for camping,
about the supply of fresh water for instance. But perhaps he had not
considered the dryness of the summer. In any case it might seem to
have been some pressing need, such as the necessity for a plentiful
supply of fresh water, which forced him immediately to make a night
march with his army. Leaving as he tells us, under Quintus Atrius,
ten cohorts, that is, as we may suppose, two cohorts from each of his
five legions, and three hundred horse to guard the ships at anchor,
and to hold the camp, hastily made between midday and midnight, in the
third watch, that is between midnight and three o'clock, he started
with his five legions and seventeen hundred horse, as he asserts, to
seek out the enemy. Something, we may be sure, more pressing than an
attack upon a barbarian foe there was no hurry to meet, must have
forced Caesar to march his army sleepless now for two nights, one of
which had been spent upon an unusual and anxious adventure at sea, out
of camp, in the small hours, into an unknown and roadless country in
search of an enemy which had taken to its native hills. The necessity
that forced Caesar to this dangerous course was probably a lack of
fresh water. He was seeking a considerable river, for the smaller
streams, as he probably found, could not suffice after a long drought
for so great a force as he had landed.

He himself asserts that he advanced "by night" across that roadless and
unknown country a distance of twelve miles. We know of course of what
the armies of Caesar were capable in the way of marching; there have
never been troops carrying anything like their weight of equipment
which have done better than they; but to march something like fifteen
thousand men and seventeen hundred horse twelve miles in about three
hours into the unknown and the dark, is an impossible proceeding. That
march of "about twelve miles" cannot have occupied less than from six
to eight hours, one would think, and the greater part of it must have
been accomplished by daylight, which would break about half-past three
o'clock. As we have good reason to think, Caesar's march, however long
a time it may have occupied, was in search of fresh water,