By the time of her launch in 1912, "Endurance" was perhaps the strongest wooden ship ever built, with the possible exception of "Fram", the vessel used by Fridtjof Nansen and later by Roald Amundsen. There was one major difference between the ships. "Fram" was bowl-bottomed, which meant that if the ice closed in against her, the ship would be squeezed up and out and not be subject to the pressure of the ice compressing around her. "Endurance", on the other hand, was designed with great inherent strength in her hull in order to resist collision with ice floes and to break through pack ice by ramming and crushing; she was therefore not intended to be frozen into heavy pack ice, and so was not designed to rise out of a crush. In such a situation she was dependent on the ultimate strength of her hull alone.