Austria had been forced by the alliance of Italy with Prussia to maintain a large force south of the Alps which would have been of priceless value at Sadowa. Against Archduke Albrecht in the Lombard plain the Italians showed little skill and were heavily defeated. On June 24 they were crushed at Custozza-already once fatal to Italian patriotic hopes. The Italian fleet too, whose superiority over the Austrian fleet was thought to be certain, was heavily defeated at the Battle of Lissa. If Italy had stood alone the work of 1859 might have been undone. But Bismarck had promised that he would make no peace which did not give Venice to Italy, and the victory of Sadowa completed the work of Magenta and Solferino.