The Convention of Reichenbach (27 June 1813) was an agreement between Austria, Prussia and Russia, in which the Austrians agreed to join the war against Napoleon unless he agreed to a series of demands.
During the spring campaign of the War of Liberation Napoleon had inflicted two defeats on the Prussians and Russians, at Lützen and Bautzen, but he was unable to turn either of these victories into the sort of decisive success he had achieved at Austerlitz or Jena/ Auerstadt. On 2 June Napoleon agreed to a temporary pause in the fighting, and on 4 June this was extended into a full armistice (Armistice of Pleischwitz). Both sides needed time to regroup after the spring campaign, although Napoleon probably came off worst from the pause, which came just as the Allies were on the brink of disaster in Silesia.
In the aftermath of the armistice both sides attempted to win over Austria, which had remained neutral throughout the spring campaign.
On 26 June the Austrian foreign minister Metternich met with Napoleon at Dresden, in a famously stormy meeting. This news was then sent east to Reichenbach, in Prussian Silesia (now Dzierzoniow in Poland) where Tsar Alexander and King Frederick William III of Prussia were based. Also present was Count Stadion, then serving as an Austrian foreign ministry advisor.
On 27 June Stadion committed Austria to joining the Sixth Coalition if Napoleon didn't agree to their terms. These were probably designed to be rejected. The Grand Duchy of Warsaw was to be abolished, with most of it going to Russia. The Confederation of the Rhine would also be abolished. Prussia would regain all of the lands lost after the disasters of 1806 (apart from in Poland). Austria would regain Illyria, on the Adriatic coast. France would also surrender all of the areas of northern Germany she had taken in 1810 (in particular Hamburg and Lübeck). However Napoleon would have been left with Italy, Belgium and the Rhine as the eastern frontier of France. In return all Metternich offered was a promise of Austrian neutrality and to mediate between France and her enemies. The Allies also agreed not to make peace with France separately.
Metternich committed Austria to joining the Sixth Coalition once Napoleon had publicly rejected the terms. There is still a great deal of controversy about Metternich's motives. The most popular view is that he deliberately chose terms he knew Napoleon wouldn't accept, especially after his victories at Lützen and Bautzen, in order to draw Austria into the war. The alternative is that the negotiations at Dresden were a genuine attempt to agree the basis for peace, and it was Napoleon's rejection of them that made up Metternich's mind.
Although Napoleon did indeed reject the Austrian terms, news then arrived from Spain of Wellington's victory at Vittoria. This encouraged Napoleon to try once more, and Armand-Augustin, marquis of Caulaincourt, was sent to Prague to resume negotiations (Congress of Prague, 15 July-10 August 1813). On 12 August 1813 Austria declared war on France, although she didn’t officially join the Sixth Coalition until the treaty of Teplitz (9 September 1813).
The talks at Reichenbach also produced treaties between Britain and Prussia and Britain and Russia, although Britain didn't sign the main Convention. On 14 June Britain agreed to pay Prussia 66,666 pounds sterling to help pay for 80,000 Prussian troops. In return Prussia gave Hildesheim and other areas to the Electorate of Hanover. On 14 June Britain agreed to pay 1,333,334 pounds sterling to Russia to help support 160,000 troops.
Some sources give a date of 19 July for the Reichenbach agreement, but this was the date on which the Prussians, Russians and Bernadotte agreed to some Austrian changes to the Trachenberg Plan, the overall Allied military plan for the autumn campaign.