 Another attack followed on 26 April 1916 on the coastal towns of Yarmouth and Lowestoft but both were important naval bases and defended by shore batteries.Unrestricted submarine warfare was instituted in 1915 in response to the British blockade of Germany and to the British Government's refusal to court-martial the perpetrators of the Baralong incidents.Prize rules, which were codified under the 1907 Hague Convention—such as those that required commerce raiders to warn their targets and allow time for the crew to board lifeboats—were disregarded and commercial vessels were sunk regardless of nationality, cargo, or destination.