90 THE THEATRE OF WAR
(b) The border hills
These were a more or less continuous chain of heights which
stretched all the way from southern Germany to Hungary and
constituted the highest ground between the northern plains and
Vienna. The people who come from this low-lying and flat
country are given to uttering a great shriek, when they catch
sight of the first hill worthy of the name. They believe they have
glimpsed the very pillars of Heaven' (Riesebeck, 1784, II, 4). It is
true that the hills were not particularly high, by Pyrenean let
alone Alpine standards, but in operational terms they consti-
tuted significant obstacles. The passes became impenetrable in
wintertime, so a commander had to establish himself solidly
and deeply on the enemy side of the heights if he was not to be
forced to retreat before the end of the campaigning season.
Moreover at every time of the year the hill country favoured the
work of the Austrian hussars and Croats who preyed on the
Prussian convoys.
(c) The Austrian provinces of Bohemia and Moravia
These two territories lay south of the hills, and exhibited a great
variety of terrain which will be investigated shortly.
To make some sense of what happened in the wars it is necessary
to rearrange our basic physical geography into strategic zones, re-
flecting the influence of forces like politics, strategies, agriculture,
and the legacy of the past in the shape of bridges and fortresses. Three
such geopolitical systems appear in the middle of the eighteenth
century:
Berlin and the eastern approachesFrederick's way of war was greatly influenced by the vulnerability of
the Brandenburg heartland. Berlin was an open city which could
scarcely be defended by less than 20,000 men, for the feeble excise
wall did not come into the reckoning. The royal residence of Potsdam
was quite untenable. Spandau, the weapons smithy of the Prussian
state, also stood open to the invader. It was true that Spandau citadel
was tactically strong, and covered by the marshes of the Spree and
Havel, but it was too small to be of any strategic account.
In the Seven Years War the Russians found it convenient to avail
themselves of the navigation of the Netze and the Warthe, and to
establish their main depot at Posen in western Poland. Thereafter
they could turn south into Silesia, or push on due west through the
Neumark of Brandenburg against Berlin. In the latter case the only