In March 1918 Horthy's position within the navy was secured, and he had begun to reorganize it according to his own vision, with strong support from Emperor Karl I. By this time, the United States had declared war on both Germany and Austria-Hungary and had begun to send ships to aid the French, British, and Italians in the Mediterranean Sea. Horthy had inherited an "Austrian lake" in the Adriatic Sea, according to the United States Navy, and shipping of supplies, troops, sick and wounded personnel, and military equipment across various ports in the Adriatic was done with little to no opposition from the Allied Powers. American planning for a naval offensive to sweep the Adriatic and even land up to 20,000 marines with naval and infantry support from Britain, France, and Italy were halted by the onset of the German Spring Offensive in France, launched on 21 March 1918. Horthy used these first few months as Commander-in-Chief to finish his re-organization of the navy. As one of Njegovan's final actions before he was ousted entailed shifting several smaller and older vessels around to different ports under Austro-Hungarian control, the only ships which remained at port in Pola aside from the three of the "Radetzky" class were the four dreadnoughts of the "Tegetthoff" class, which had now fallen under the command of Captain Heinrich Seitz. Horthy worked to re-locate as many ships as he could back to Pola in order to maximize the threat the Austro-Hungarian Navy posed to the Allied Powers. Horthy also used his appointment to take the Austro-Hungarian fleet out of port for maneuvers and gunnery practice on a regular basis. The size of these operations were the largest the navy had seen since the outbreak of the war.