In November 1924, Kongo docked at Yokosuka, where modifications were made to her main armament, increasing the elevation of her main guns and improving her fire-control systems. In 1927, Kongō underwent major modifications to her superstructure, rebuilding it into the pagoda mast style to accommodate the growing number of fire-control systems for her main guns. In May 1928, her steering equipment was upgraded, before she was placed in reserve in preparation for major modifications and reconstruction in 1929–31. 1929–1935: Reconstruction into battleship Prohibited by the Washington Treaty from constructing new capital ships until 1931, Japan resorted to upgrading their World War I era battleships and battlecruisers. Beginning in September 1929, Kongō underwent extensive modernization and modification in drydock at Yokosuka Naval Arsenal. Over the next two years, Kongōs horizontal armor near her ammunition magazines was strengthened, and the machinery spaces within the hull were given increased torpedo protection. Anti-torpedo bulges were added along the waterline, as permitted by the Washington Treaty. She was refitted to accommodate three Type 90 Model 0 floatplanes, though no aircraft catapults were fitted. To increase her speed and power, all 36 of her Yarrow boilers were removed, and then replaced with 16 newer boilers, and Brown-Curtis direct-drive turbines were installed. Kongōs forward funnel was removed, and her second funnel was enlarged and lengthened. The modifications to her hull increased her armor weight from 6,502 to 10,313 long tons, directly violating the terms of the Washington Naval Treaty. In March 1931, Kongō—now capable of a speed of —was reclassified as a battleship. On 22 April 1930, Japan signed the London Naval Treaty, placing further restrictions on the signatories' naval forces. Several of her older battleships were scrapped, and no new capital ships were built as replacements. After minor fitting-out work, Kongōs reconstruction begun in September 1929 and was declared complete on 31 March 1931. On 1 December 1931, two months after the Japanese invasion of Manchuria, Kongō was assigned to the First Battleship Division and also designated the flagship of the Combined Fleet. Additional rangefinders and searchlights were fitted to her superstructure in January 1932, and Captain Nobutake Kondō assumed command of the vessel in December. In 1933, aircraft catapults were fitted between the two rear turrets. On 25 February 1933, following a report by the Lytton Commission, the League of Nations agreed that Japan's invasion of China had violated Chinese sovereignty. Refusing to accept the