Union of Lublin  Union of Lublin, (1569), pact between Poland
and Lithuania that united the two countries into a single state.
After 1385 (in the Union of Krewo) the two countries had been
under the same sovereign. But Sigismund II Augustus had no
heirs; and the Poles, fearing that when he died the personal
union between Poland and Lithuania would be broken, urged that a
more complete union be formed. After the Livonian War began
(1558) and Muscovy presented a serious threat to Lithuania, many
of the Lithuanian gentry also desired a closer union with Poland
and in 1562 made a proposal for merging the two states. The
dominant Lithuanian magnates, however, feared that a merger
would diminish their power and blocked the proposal as well as
subsequent initiatives. When representatives from both countries
at a meeting of the Sejm (legislature) at Lublin (January 1569)
failed to reach an accord, Sigismund II annexed the Lithuanian
provinces of Podlasie and Volhynia (including the regions of
Kiev and Bracław), which