The crushing defeat of Italian forces at the Battle of Novara (23 March 1849) sounded a death knell for Italian independence from the Austrians. To avoid an occupation of Piedmont, Charles Albert abdicated in favour of his son Victor Emmanuel II, whose treaty with Austria required the complete removal of the Sardinian navy from Venetian waters. Manin addressed the Venetian assembly on 2 April 1849 and they voted to continue their struggle against the Austrians, despite an Austrian blockade of the city. On 4 May 1849, Radetzky started his attack on the Venetian fort of Marghera, held by 2500 troops under the Neapolitan command of Girolamo Ulloa. Bombardment of the lagoon and city started at the same time and, over the next three weeks alone, were dispatched towards Venice. The fort at Marghera held out until 26 May, when Ulloa ordered its evacuation; an offer of surrender from Radetzky was rejected at this time.