Following a series of provocative military movements near the Austro-Piedmontese frontier by Piedmont-Sardinia, and having become aware of the Franco-Sardinian alliance, the Austrians took the initiative by issuing the Ultimatum of Vienna on 23 April 1859. The Austrian ultimatum required the total demobilisation of the Piedmontese army. By failing to comply with this demand, the Piedmontese triggered a declaration of war by Austria, thereby fulfilling the French condition that their support for Piedmont-Sardinia would be contingent on Austria being the aggressor in any war.