After the fall of Prague Frederick lay in the centre of Bohemia, a kingdom walled in by a quadrilateral of mountains. He held the north-eastern gates which led into Silesia. The south-western led into Bavaria, and through them the army of Alsace was soon to enter. But at the head of nearly 80,000 men the King was vastly stronger than any single force that could be brought against him and his communications with Prussia were safe. There was therefore much to be said for a simple defensive policy. North-eastern Bohemia was the prize that Frederick hoped to gain by the war, and this he could have held like a second Silesia. Such a desertion of his allies would, however, have shocked public opinion, particularly in France, and Frederick admits that he shrank from it on that account.
The next best course, if some offensive movement must be made, would have been first to crush the army of Bohemia and then to hold the south-western gate against the army of Alsace. This course was advised by Schwerin and favoured by the King. But the fatal influence of Belleisle proved stronger than the promptings of common-sense. France was avenged for the treacheries of Klein Schnellendorf and Berlin when Frederick allowed himself to be persuaded to strike due south, in the hope of conquering Bohemia, opening communications with Bavaria, and cowing Vienna.
At first the plan prospered. Several towns were captured for the Emperor, and by October 4, 1744, the Prussians had almost reached the frontier of Austria proper. Then they began to realise that they were the dupes of a mirage. The armies of Bohemia and of Alsace had united in their rear and lay between them and Prague. They found themselves isolated, ill fed, and worse informed. Swarms of light horse enveloped them, cutting off convoys, scouts, and messengers. Schwerin opened a line of retreat, but their recent conquests were lost with the garrisons which held them. The Austrians had found a soldier, Field-marshal Traun, and at his hands Frederick received painful lessons in the art of war. The King had already begun to negotiate. He thirsted for French co-operation and a pitched battle, but could obtain neither boon. Traun, who was now superior in numbers, had no need to fight. He occupied unassailable positions to the north of Frederick’s force and left hunger, disease, and irregulars to do their work upon the enemy. Thus harassed, the Prussian rank and file deserted by thousands, and many offered their services to Traun. Schwerin again took umbrage and withdrew from the campaign.