On 10 April 1941, four days after the invasion of the Kingdom of Yugoslavia by the Axis powers commenced, an extreme Croat nationalist and fascist "Ustaše"-led puppet state was created. Known as the Independent State of Croatia (often called the NDH, from the ), it combined almost all of modern-day Croatia, all of modern-day Bosnia and Herzegovina and parts of modern-day Serbia into an "Italian-German quasi-protectorate". Germany and Italy quickly agreed on their division of responsibility within the NDH, and effectively occupied the entirety of the country, but the Germans retained the upper hand and control over the most industrially and agriculturally productive parts of the puppet state, despite assuring the Italians that the NDH was in their sphere of influence. The Germans gradually increased their domination over the NDH as time passed, while the Italians were unpopular among the Croat population because they annexed large parts of Croatian territory, including much of the Adriatic coastline. As the weaker Axis partner, Italy was unable to challenge Germany's grip on the NDH, and the "Ustaše"-led Croats had to accept whatever conditions were imposed on them. By long-standing agreement between the "Ustaše" leadership and Italy that preceded the outbreak of World War II, if the Croats ceded the Croatian coast to them, the Italians would provide for its protection.