On 1 October 1766, aged twenty, he married Princess Sofie
        Magdalene of Denmark but it took twelve years before his son and heir
        was born. A little over four years after his marriage on 12 February
        1771, he succeeded his father as King of Sweden. On 19 August 1772 he
        staged a bloodless military coup to reverse the constitutional
        provisions of the 'age of liberty'. The powers of the crown were
        restored, the senate arrested and the Riksdag reconvened.
            On 21 August 1772 the new constitution was approved. The king
        regained the power to summon and dismiss the Riksdag, to appoint
        ministers and to propose legislation. An enlightened despot, he
        introduced reforms including reform of the currency, reduction in the
        number of capital offences, and limited religious toleration.
            His difficult, restless temperament made Gustaf prefer to work
        with favourites rather than through his council. In later years he
        became increasingly interested in bolder foreign policy. Prevented
        from invading Norway in 1784 by Russian pressure, he attacked Russia
        in 1788; but the war, which ended in 1790, did not live up to his
        expectations and precipitated domestic tension in Sweden, especially
        among the Finns.
            To break his opponents, he started a new constitutional coup in
        1789, pushing through an Act of Union and Security. Under this the
        estates lost all their legislative initiative while the crown's power
        to introduce laws was considerably extended. Most public offices were
        opened to commoners, while peasant's rights to purchase land were
        extended.
            Greatly affected by the French Revolution, Gustaf made plans to
        act against France. However, an aristocratic conspiracy led to his
        mortal wounding at a masked ball by Johan Jakob Anchorstrom on 16
        March 1792. He died on 29 March 1792.
 

Source: Leo van de Pas