It was no longer possible to resist Russia's claims on Poland, but Austria was determined not to allow Prussia to receive the proffered compensation. On December 10 Metternich notified the Prussian minister, Hardenberg, that he would not allow Prussia to annex more than a fifth part of Saxony. Great Britain, France, Bavaria, and the minor German states joined Austria in this action, and thus the attempt to effect a settlement of Europe by a concert of the four allied powers broke down. On January 3, 1815, a secret treaty was concluded between Austria, France, and Great Britain in defence of what their diplomatists called "the principles of the peace of Paris". Each of these powers was to be prepared, if necessary, to place an army of 50,000 men in the field. Bavaria joined them in their preparations for war, and many of the troops which occupied Paris in 1815 would have been disbanded or dispersed, but for the prospect of a rupture between the allies themselves. But a compromise was soon arranged, and on February 8 it was agreed that Cracow, the Polish fortress which threatened Austria most, should be an independent republic, and that Prussia should retain enough of Western Poland to round off her dominions, while the remainder of the duchy of Warsaw became a constitutional kingdom under the tsar. Prussia was to be allowed to annex part of Saxony, and was to receive a further compensation on the left bank of the Rhine and in Westphalia. The most thorny questions were now settled, and Castlereagh had left Vienna when the congress was electrified by the news that Napoleon had reappeared in France.