At this time, the Ottoman Empire was in expansion and making its power noticeable in the Mediterranean and North Africa. At the same time, the Aragonese Mediterranean Empire was crumbling under debt and war exhaustion. Ferdinand reasonably feared that he would not be capable of repelling an Ottoman attack to Spain's shores, especially if the Ottomans had internal help. The regions with the highest concentration of Moriscos were those close to the common naval crossings between Spain and Africa. If the weakness of the Aragonese Naval Empire was combined with the resentment of the higher nobility against the monarchs, the dynastic claims of Portugal on Castile and the two monarch's exterior politic that turned away from Morocco and other African nations in favor of Europe, the fear of a second Muslim invasion, and thus a second Muslim occupation was hardly unfounded. This fear may have been the base reason for the expulsion of those citizens who had either a religious reason to support the invasion of the Ottomans (Moriscos) or no particular religious reason to not do it (Jews). The Inquisition might have been part of the preparations to enforce these measures and ensure their effectiveness by rooting out false converts that would still pose a threat of foreign espionage.