During the interwar period the campaign "became a focal point for the study of amphibious warfare" in the United Kingdom and United States, because it involved the four types of amphibious operations: the raid, demonstration, assault and withdrawal. Analysis of the campaign before World War II led to a belief among many armed forces that amphibious assaults could not succeed against modern defences. The perception continued until the Normandy Landings in June 1944, despite some successful examples of amphibious operations earlier in the war, such as those in Italy, and at Tarawa and in the Gilbert Islands in the Pacific. Although the negative perception prevailed among Allied planners in the interwar years, the war situation after 1940 meant that such operations had to be considered. However, despite early successes in North Africa and Italy, it was not until Normandy that the belief that opposed landings could not succeed was completely excised.