The War of the Bavarian Succession formally began, however, when Frederick set out for Bohemia, on July 3, 1778. He was attacking with two armies, each about 80,000 strong. Earlier in the year he had hoped that the main Austrian force would assemble in Moravia. In that case his plan was to lead his own army from Silesia against it, to win a great victory, and thus to compel the enemy to call back their troops from Bohemia. This would make it easy for Prince Henry with a combined host of Prussians and Saxons to advance on Prague while the King made progress in Moravia. The two armies, if all continued to go well, would then press forward towards the Danube. The plan was spoiled, however, because the Austrians were bold enough to choose north-eastern Bohemia for their place of concentration. There they were indeed further from Vienna, but they secured greater possibilities of offensive action. If Frederick invaded Moravia they could overrun Silesia behind his back or fall upon Prince Henry and Saxony in overwhelming force. The King, therefore, reluctantly turned aside into Bohemia by way of Nachod in order to engage the enemy’s attention until his brother, marching from Dresden, should have established himself firmly in the north. On his arrival in Bohemia, Frederick found the Austrians some 250,000 strong. Joseph and Lacy with the bulk of the troops confronted him in a position on the Elbe nearly fifty miles in length and as strong as water, earthworks, and cannon could make it. Judging it impregnable, Frederick waited impatiently for his brother to get the better of Laudon, who was guarding the northern gate into Bohemia. The army chafed at the enforced inaction, but the King still hoped by sending repeated detachments to Moravia to compel the enemy to meet him there in the field. Prince Henry, after hesitating for some time between different routes, performed his task to perfection. Early in August he led his army over the mountains to the east of the Elbe by ways hitherto reputed impassable. Laudon was at his wits’ end. He fell back upon the line of the Iser, but on August 14th, Joseph himself admitted that he was too weak to hold it. If Laudon were driven off, the great position on the Elbe would be untenable, but Prince Henry lacked the hardihood to venture the decisive move. Dissensions between the royal brothers and the failure of their efforts to effect a junction justified the policy of their opponents, who, Frederick sneered, seemed to be turned into stone. Soon the movements of the Prussians were dictated largely by hunger and the conflict earned its nickname of the Potato War. Heavy rains completed their discomfiture. By the middle of October the exultant Austrians had seen the last of the invaders.