At the conclusion of the armistice in 1632, during a short interregnum in Poland, he attempted to avenge past injuries and recover lost territory; but the campaign was not successful, and in 1634 he signed a definitive treaty by no means favourable to Russia.
He was now one of the most powerful sovereigns of Europe, for besides ruling over Provence and Anjou and the kingdom of the Two Sicilies, he was imperial vicar of Tuscany, lord of many cities of Lombardy and Piedmont, and as the pope's favourite practically arbiter of the papal states, especially during the interregnum between the death of Clement IV.
The election of Rudolph of Habsburg as German king after a long interregnum, and that of Nicholas III.
Of course, generally speaking, less advance was made than in many previous decades, owing to the interregnum caused by the World War, when all British, French, German, and Austrian work was held up, and only the Americans and to a lesser degree the so-called " Egyptian " Service of Antiquities (manned by French and English) did any digging at all; while in all the European countries the energies of all the archaeologists who were not superannuated were transferred to the field of war, and there was no time left to write little papers, still less big books.
During the ensuing interregnum he powerfully contributed, at the head of the nobles of Funen and Jutland, to the election of Christian III.