Page 612

 612 A HISTORY OF THE CRUSADES 
the elector of Saxony, and had therefore been occupied by Saxon troops. But
in June 1426 a strong Hussite army began to besiege Usti, and the Saxon rulers,
with the elector's wife Catherine espe cially active, sent a large army to
raise the siege and safeguard Saxony's possession of this important Elbe
town. The Saxon army— until then considered among the best—was
certainly larger than the Hussite army of about 24,000 men, under the overall
command of Korybut, with Prokop commanding the Taborite forces. Apparently
none of the previous battles fought between Germans and Czechs had resulted
in losses as catastrophic as the battle of Usti, even though the assertion,
made by German chroniclers, that the German dead numbered 15,000 was probably
much exaggerated. Prokop, after the victory, tried to convince the other
commanders that this was the right moment to enter Saxony in "hot pursuit"
and reduce that country's war-mindedness, but as yet without success. 
Even so it seemed likely, in the eyes of the Germans, that the terrible heretics
would not wait long before crossing the border. If the idea of destroying
the "heresy" was not to be given up for good, preparation for a new crusade
could not long be postponed. Modest invasions of Silesia and Austria were
undertaken by Czech-Hussite troops in the winter of 1426—1427, and
in March 1427 a Taborite army under Prokop defeated an Austrian army, causing
it heavy losses, at the Austrian town of Zwettl,68 midway between Budweis
and Vienna. It seemed increasingly doubtful whether the margraviate of Moravia,
solemnly presented to duke Albert by his father-in-law Sigismund, could be
maintained in Hapsburg hands. In addition, some vague possibilities for an
understanding between the Catholic powers and the conservative Hussite elements,
rather strongly repre sented by some of the masters of Prague University
and some nobles, collapsed when negotiations with Rome secretly conducted
by Kory but were discovered in April 1427. The more determined Utraquists,
with John Rokycana at their head, undertook to prevent what seemed to them
pure treason.69 The prominent conservatives, among them the masters at the
University who had supported a policy of compromise or even submission, were
banished from Prague, and Korybut not only lost his already somewhat enfeebled
position as regent but was even imprisoned for several months. 
It was not, however, this development which led to the final decision for
a fourth crusade. This had already been decided upon at the very beginning
of the year, at a rather remarkable meeting at 
68. Macek, Prokop Veliky, pp. 52—53. 
69. Bartos, Husitska revoluce, II, 19—22.