Defeated warlord Zhang Zongchang would return to his former territory of Shandong in 1929, where he launched a rebellion against his former subordinate Liu Zhennian, who had defected to the nationalists during the Northern Expedition. While the rebellion was put down swiftly, it demonstrated the Nanjing government's shaky hold on China's vast territory. As Chiang attempted to cut back the military and centralise the power of the nationalist government in Nanjing, the regional warlords, with their military forces largely intact, began to renounce their allegiance to Chiang and form an alliance against the KMT. This struggle for supremacy broke into armed conflict in the Central Plains War of 1929–30. Although Chiang was ultimately victorious in that war, ensuring his status as singular leader of all China, regionalism and warlordism would continue, weakening the country and laying the groundwork for the Second Sino-Japanese War and the Chinese Civil War.