several synonyms representing regional descriptors for a goshawk; Accipiter, Bolesta, Boleścic, Jastrząb, Jastrząbek, Kamiona, Łazęka, Lubrza. During the 11th and 12th centuries, the Polish state was fragmented amongst rival Royal Dukes, causing instability. The szlachta including the Jastrzebiec, in turn formed a stable and successful semi-feudal backbone allowing a decentralised state to evolve. This subsequently resulted in many new branches of the szlachta, in the 13th century, which now comprised up to 10% of the population. For example, the subsequent 'Jankowski branch' of the Jastrzebiec descendants (written Jankowski herbu Jastrzebiec) were probably resident in the region of Łomża (North Eastern Poland), from the villages of Jankowo Młodzianowo and Jankowo Skarbowo. In the following decades, the immediate descendants of this Jankowski family also held lands further north and east, south of Vilnius (now Lithuania), west of Minsk (now Belarus), and near the town of Suwałki (still in Poland). The nobility including the Jankowski h. Jastrzebiec were given special impetus by Casimir III the Great in the early 14th century who formally adopted them as 'leaders of warriors' to replace the levée en masse used by previous kings. It is likely that a proportion of Jankowski lands were in part granted to family members by the Kings of Poland following acts of military devotion to the state against the many hostile invaders including Germans, Teutons, Russians, Mongols and Tatars. Migration The Jankowski h. Jastrzebiec family members adapted to the local Eastern European customs and language and are now also known by the Lithuanian form Jankauskas and in the Russian Cyrillic form as Янковский. Progressive eastward migration was particularly prominent from the 15th century onwards, when the Treaty of the Union of Horodło was signed, granting Polish nobility the freedom to settle in the vast underpopulated fringes of Lithuania and Belarus. This was further endorsed by the Union of Lublin a century later. The 16th century was also in many ways the golden age of Poland with the rural agricultural economy booming especially with grain exports to central and western European markets as well as Britain. In this period the Jankowski family consolidated their position and expanded their lands and with surplus income educating their families in the Renaissance style. In the 17th century, the Polish–Lithuanian Commonwealth was now the largest country in the whole of Europe and the decentralised nature of the country's government relied on semi-autonomous distinct regional principalities. Therefore, while