His request being granted, Languet spent the last years of his life mainly in the Low Countries, and though nominally still in the service of the elector, he undertook a mission to England for John Casimir of Bavaria and was a valuable adviser to William the Silent, prince of Orange.
Indeed, from first to last, the Polish gentry as a body took good care to pay and fight as little as possible, and Casimir depended for the most part upon the liberality of the Church and the Prussian towns, and the valour of the Hussite infantry, 17c,000 of whom, fighting on both sides, are said to have perished.
Count Casimir Batthyany attacked him in The Times, and Szemere, who had been prime minister under him, published a bitter criticism of his acts and character, accusing him of arrogance, cowardice and duplicity.
Casimir Dudevant, whom she married on the 11th of December 1822, was the natural son of a Baron Dudevant.
At the same time negotiations were successfully carried on with John Casimir, with Elizabeth and with Henry of Navarre, and their help secured for the national cause.