The year 2012 marks the centenary of the tragic sinking of the Titanic on her maiden voyage. Her loss, along with more than 1,500 of her crew and passengers, remains the most famous ocean liner disaster. The story has been retold countless times, but what is less known is the ship’s place in the history of the ocean liner.

Focusing on the disaster alone leaves some obvious questions unasked, chief among them: What would the ship have done if it hadn’t hit an iceberg? We can answer that because the Titanic was the second of three sister-ships. The younger Britannic was still unfinished at the start of World War I. She entered service as a hospital ship in the Mediterranean, where she struck a mine and sank in 1916. Thirty men were lost, but more than a thousand were rescued.

But the distinguished career in peace and war of the older Olympic (1911-35) suggests that the three ships were simply unlucky, rather than poorly built. She survived a collision in 1911 with a Royal Navy cruiser; in 1918 she rammed and sank a German U-boat; and in 1934 she accidentally hit and sank the lightship Nantucket.