On 17 August, Steinbauer and UB-47 achieved their first success when they sank the Italian steamer Stampalia south of Cape Matapan.[14] Although Italy and Germany would not formally be at war for another ten days,[15] German U-boats in the Mediterranean routinely attacked Italian vessels by posing as Austro-Hungarian submarines and flying the ensign of that country's navy.[16] Stampalia was an ocean liner of 9,000 gross register tons (GRT) that had formerly been in passenger service between New York and Genoa, and had been one of the first Italian merchant vessels to be armed against submarine attacks.