Now I Rise (The Conqueror's Saga 2) - Page 127
trebuchet: A medieval engine of war with a sling for hurling large stones
vaivode: Warlord prince of Wallachia
vassal state: A country allowed to retain rulership but subject to the Ottoman Empire, with taxes of both money and slaves for the army
vizier: A high-ranking official, usually advisor to the sultan
Wallachia: A vassal state of the Ottoman Empire, bordered by Transylvania, Hungary, and Moldavia
Source: readsnovelonline.net