Treaty of Monçon

The Treaty of Monçon or Treaty of Monzón was signed on 5 March 1626 by Cardinal Richelieu, the chief minister of Louis XIII and Gaspar de Guzmán, Count-Duke of Olivares, the chief minister of Philip IV of Spain, at Monçon (modern Monzón) in Aragon. It was signed in the aftermath of the French capture of Valtelline from Papal troops, and also concluded the First Genoese-Savoyard War.

Valtelline, in Northern Italy, was vitally important to the communications between the Spanish and Austrian branches of the House of Habsburg. The Sforzas had ceded the territory to the Grison League, but there were religious conflicts due to Valtelline natives being Catholic and their Grison masters being Protestant. Seeing an opportunity, the Spanish incited a revolt in Valtelline and eventually controlled the valley. Realizing the danger, in 1623, Venice, the Duke of Savoy, and France formed an alliance to capture this strategic position in signing the Treaty of Paris (1623). Spain tried to maintain peace by allowing the Papacy, over which they had great influence, to control it. France did nothing as the Papal troops of Gregory XV established control over Valtelline due to the lackluster policies of Charles de la Vieuville. Gregory XV was soon afterwards succeeded by Pope Urban VIII

With the ascendancy of Richelieu, French policy changed. They claimed that due to the alliance between them and the Duke of Savoy, they had to help Savoy who were attacking Genoa, by attacking Valtelline and diverting the resources of the Spanish, who were supporters of Genoa. In 1624, French troops quickly expelled Papal troops from the valley. The irony of a Cardinal attacking the troops of a Pope was not lost on Rome, Spain, and ultra-Catholics in France.

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