The only son of a nobleman, he finalised his education by travelling in Western Europe. Caught up in the continual conflicts between the Northern European nations, Poland was invaded in 1702 by King Charles XII of Sweden. This king forced the Polish nobility to depose King Augustus II (Friedrich August I of Saxony) and in 1704 placed Stanislas Leszczynski on the throne.
Foreign armies marched through and ravaged Poland at will. In 1709 Charles XII was defeated by the Russians and forced to withdraw to Sweden, leaving Stanislas without any support. Augustus II returned to the Polish throne while Stanislas went into exile to settle in France.
In 1725 his daughter, Marie, married the French King Louis XV and, in 1733 when Augustus II died, Stanislas returned in secret to Poland and was elected King. However, before he could be crowned, Russia and Austria invaded the country and once more he was forced into exile. He fled from Warsaw before the city was taken by the Russians, going to Königsberg in Prussia from where he directed guerilla warfare against the new king, Augustus III. However, the Peace of Vienna in 1738 recognised Augustus III as King of Poland, while allowing Stanislas to retain his royal title. As well, he was given the duchies of Lorraine and Bar for life.
He proved to be a good administrator and promoted economic development, while his court in Lunéville became a cultural centre. He founded an academy of science at Nancy and a military college. In 1749 he published a book, 'Free Voice to Make Freedom Safe', which outlines his proposed changes to the Polish constitution. (Encyclopaedia Britannica)