In order to establish a zone of buffer states, Sigismund I of Hungary tried to draw the neighboring Orthodox rulers under his own suzerainty by granting them estates in his kingdom. For example, Stefan Lazarević of Serbia received Satu Mare, Baia Mare and Baia Sprie in modern Romania, and Mircea I of Wallachia was granted Făgăraş. Sigismund I was also the first monarch who recognized, in 1419, the legislative competence of the Estates in Transylvania. On his initiative, their assembly declared that in case of an Ottoman attack, every third nobleman and every tenth serf would take up arms. Indeed, from 1420 Ottoman attacks occurred on an annual basis. In this period many Saxon churches, and later the Székely churches of the Ciuc region, were fortified, which gave local architecture a distinctive appearance.