Gustavus timed his invasion with great judgment. The diet of Regensburg was still sitting, and the army of Wallenstein was demoralised by the approaching sacrifice of its chief. Hardly a month after the landing of the Swedish king that sacrifice was consummated, a large part of Wallenstein’s army was disbanded, and the rest put under the command of Tilly, who was becoming in his old age extremely dilatory in his movements. Gustavus accordingly found himself for six months practically unopposed, and he at once employed the time in establishing for himself a strong basis of operations on the Baltic and in the enlistment of fresh troops. In January of the next year came a most welcome assistance. Richelieu had long fixed his eyes upon Gustavus, as one of the most formidable weapons capable of being used against the House of Austria, and he desired to put it into the armoury of France. Negotiations had been opened with this object in the spring of the year but had failed. [Sidenote: =Alliance between Gustavus and Richelieu, 1631.=] He had found Gustavus more stubborn than he had expected, and quickly realised that if he wanted the king of Sweden’s help he could have it only on the king of Sweden’s terms. Gracefully submitting to the inevitable, on January 23rd 1631 he concluded with Gustavus the treaty of Bärwalde, by which he undertook to supply the king with 200,000 dollars for six years, on condition that Gustavus maintained an army of 36,000 men, promised to respect the imperial constitution, observed neutrality towards Bavaria and the League as far as they observed it towards him, and left the Catholic religion untouched in those districts where he found it established. The alliance of the foreigner was the only voluntary aid which the liberator of Germany could obtain. [Sidenote: =Jealousy of Gustavus in Germany.=] The old duke Boguslav of Pomerania was as submissive in the hands of Gustavus as he had been in the hands of Wallenstein, but it was helplessness not friendship which put his resources at the disposal of the invader. John George of Saxony and George William of Brandenburg steadily refused to break their neutrality, or take one step in the direction of the dismemberment of the Empire. In March a great gathering of Protestants was held at Leipzig to consider the situation. They agreed to raise troops for their own defence in case they were attacked. They assured the Emperor of their continued loyalty, if only he would withdraw the Edict of Restitution. They said not one word about assistance to the foreigner. [Sidenote: =The campaign of 1631.=]