On October 18, the kingdom's eastern territories, including Transylvania, swore allegiance to the infant king at the Diet of Debrecen (Hungary). Thus a separate country started to emerge, although George Martinuzzi was still negotiating with Ferdinand I on the reunification of the kingdom. For this purpose, in 1551 Ferdinand I sent an army into Transylvania where he was recognized as sole ruler by the Diet. The Ottomans, however, occupied a great part of Banat in 1552, and neither could Ferdinand I consolidate his rule over the kingdom's eastern territories. Finally, the Diet, meeting in Sebeş on March 12, 1556, swore again allegiance to "the son of King John", thus the young king and his mother returned to Transylvania.