In April 1543 Suleiman launched another campaign in Hungary, bringing back Bran and other forts so that much of Hungary was under Ottoman control. As part of a Franco-Ottoman alliance , French troops were supplied to the Ottomans in Hungary: a French artillery unit was dispatched in 1543-1544 and attached to the Ottoman Army. In August 1543, the Ottoman succeeded in the Siege of Esztergom The siege would be followed by the capture of the Hungarian coronation city of Székesfehérvár in September 1543. Other cities that were captured during this campaign are Siklós and Szeged in order to better protect Buda. However, continuous delay of the push toward the west, because of the siege of these fortresses, meant that the Ottomans could not launch any new offensive against Austria. From 1548 to the end of the war, a Habsburg Spanish infantry tercio which had fought in the Schmalkaldic War, led by Maestre de campo Bernardo de Aldana, was detached in Hungary to fight against John Zápolya's supporters on behalf of Ferdinand. In fact, the Holy Roman Emperor Charles V sent Spanish troops to help his brother regularly from 1527 to 1553, a support that proved instrumental in Hungary remaining inside Christianity.. What other country were the Ottomans attempting to conquer?