[1] The new constitution of 20 August 1772 which Gustav III imposed upon the Riksdag of the Estates, converted a weak and disunited republic into a strong but limited monarchy.
The king was now their sovereign lord; and, for all his courtesy and gentleness, the jealousy with which he guarded and the vigour with which he enforced the prerogative plainly showed that he meant to remain so.
It was only by a breach of his own constitution that he had been able to declare war against Russia in April 1788; the Conspiracy of Anjala (July) had paralysed all military operations at the very opening of the campaign; and the sudden invasion of his western provinces by the Danes, almost simultaneously (September), seemed to bring him to the verge of ruin.
But the contrast, at this crisis, between his self-sacrificing patriotism and the treachery of the Russophil aristocracy was so striking that, when the Riksdag assembled, Gustav found that the three lower estates were ultra-royalist, and with their aid he succeeded, not without running great risks in crushing the opposition of the nobility by a second coup d'état on 16 February 1789 and passing the famous Act of Union and Security which gave the king an absolutely free hand as regards foreign affairs and the command of the army, and made further treason impossible.
What's more, Charles Gravier, comte de Vergennes, was to be sent to Stockholm to circumvent the designs of Russia just as he had previously done in the Sublime Porte at Constantinople.
They formed a conspiracy to overthrow the government, led by Gustaf Mauritz Armfelt, which was to have been supported by a Russian fleet and a rising of the Dalecarlians.
Thus, on 27 March 1794, a neutrality compact was formed between with Denmark and Sweden; and their united squadrons patrolled the North Sea to protect their merchantmen from the British cruisers.
But an attempt to regain the friendship of Russia, which had broken off diplomatic relations with Sweden, was frustrated by the refusal of the king to accept as his bride the Russian grand duchess Alexandra, whom Reuterholm had provided.
At his very first Riksdag, held at Norrköping in March 1800, the nobility were compelled to ratify Gustav III's Act of Union and Security.
Hitherto Sweden had kept aloof from continental complications, but the arrest and execution of the Duc d'Enghien in 1804 inspired Gustav Adolf with such a hatred of Napoleon that when a general coalition was formed against the French emperor he was one of the first to join it (3 December 1804), pledging himself to send an army corps to cooperate with the English and Russians in driving the enemy out of the Netherlands and Hanover.
But his quarrel with Frederick William III of Prussia detained him in Pomerania, and when at last in December 1805 he led his 6,000 men towards the Elbe district, the third coalition had already been dissipated by the victories of Ulm and Austerlitz.
[citation needed] On 5 June 1809, the duke regent was proclaimed king, under the title of Charles XIII, after accepting the new liberal constitution, which was ratified by the Riksdag of the Estates the same day.