The Convention of Turin of 1742, in which Austria allied with the Kingdom of Sardinia, caused some consternation in the Republic. However, when this provisional relationship was given a more durable and reliable character in the signing of the Treaty of Worms, in 1743, the fear of diplomatic isolation had caused the Genoese Republic to abandon its neutrality and to ally with the House of Bourbon in the War of the Austrian Succession. Consequently, the Republic of Genoa signed a secret treaty with the Bourbon allies of Kingdom of France, Spanish Empire and Kingdom of Naples. On 26 June 1745, the Republic of Genoa declared war on the Kingdom of Sardinia. This decision would prove disastrous for Genoa, which later surrendered to the Austrians in September 1746 and was briefly occupied before a revolt liberated the city two months later. The Austrians returned in 1747 and, along with a contingent of Sardinian forces, laid siege to Genoa before being driven off by the approach of a Franco-Spanish army.