 Submarines, however, depending on stealth and incapable of withstanding a direct attack by a surface ship (possibly a Q-ship disguised as a merchant ship), found it difficult to give warning before attacking or to rescue survivors, which meant that civilian death tolls were high.This was a major factor in galvanizing neutral opinion against the Central Powers, as countries like the United States suffered casualties and loss to their trade, and was one of the causes of the eventual entry of the US into the war.In "Sovereignty at Sea