Before the adoption of the present Convention there was controversy as to whether or not undefended ports, towns and buildings might be bombarded by naval forces. There was a difference of opinion as to whether the rule applicable in land warfare prohibiting bombardment of undefended towns (Article 25 of the Hague Regulations of 1899 and 1907) was also applicable to bombardment by naval forces. The Institute of International Law, in 1896, declared that the law relating to bombardment was the same in land and sea warfare. This view, however, was not accepted by the Powers at the Second Hague Peace Conference. Although Article I of the present Convention confirms the principle that undefended ports and towns may not be bombarded, Article 2 allows bombardment by naval forces of military objectives in undefended towns. This new rule eventually became applicable in air warfare, too.
D.Schindler and J.Toman, The Laws of Armed Conflicts, Martinus Nijhoff Publisher, 1988, pp.812-815.