_ „., THE THEATRE OF WARoperating from there we can make the Austrians fear for the
safety of Vienna, which is of a different order of importance for
the House of Austria than Prague. (To Henry, 2 June 1778, PC
26422)Inside Moravia the only obstacles to Prussian progress were artificial
ones, namely the old fortress town of Briinn, and Olmiitz with the
new works which were built before the Seven Years War.
In this way the Silesian strategic system reached well into
Moravia. It also marched with north-eastern Bohemia. Along this
sector the County of Glatz formed a strategic appendix or sub-system.
Its southern and eastern rims were high and mostly inaccessible. The
corresponding northern side was screened from Lower Silesia by the
Eulen-Gebirge, which was of no great height, but very precipitous
and thickly wooded. The Eulen-Gebirge was to prove an embarrass-
ment to Frederick in his later campaigns, for if he was off his guard the
Austrians could gain the passages of Wartha and Silberberg in a
couple of marches from the Silesian border, and so effect an entry to
the Silesian plain. This was why Frederick built a fortress at Silber-
berg after the Seven Years War.
Offensively, the County of Glatz offered Frederick a choice of
routes either due west up the steepish path over the border and then
down to Nachod, or more conveniently by the broad valley to
Braunau.
At Nachod and Braunau we meet what was by far the most
important of the corridors between the Prussian and Habsburg states.
At the northern end it brought the Austrians into the heart of Silesia
close to Breslau, and 'Lower Silesia is the vital part of the duchy. We
must hang on to it' (Frederick to Schwerin, 2 August 1956, PC 7796).
At the southern end the avenue extended into north-eastern Bohemia
by way of Koniggratz and Pardubitz.
In Lower Silesia Frederick owned two strategic bulwarks towards
the border hills. Schweidnitz (fortified from 1747) stood in a fertile
region an easy twenty-five-mile march from the Oder. 'It has the
highest steeple in all Silesia, and from which there is an extensive and
beautiful prospect over the wide plains which surround the town to
the distant mountains, which look like a wall round the horizon'
(Adams, 1804, 185).
In 1745, and in almost every campaigning season of the Seven
Years War, the armies contested for the piedmont region above
Schweidnitz and Hohenfriedeberg, where the rounded bosky foothills
of the Riesen-Gebirge swept down to the plain and interlocked with
the green fingers of the valleys reaching into the higher ground.
It was hard to evict the Austrians when they emplaced themselves