The turnover of arguably China's most powerful position, the chairmanship of the Central Military Commission, which controls the armed forces, marks the end of the leadership change that began in late 2002.
The shift, though important for the smooth working of the Chinese government, was not likely to cause any radical changes in its relations with the United States, its drive to reincorporate Taiwan into mainland China, or its effort to move the nation toward a market economy while maintaining growth and social stability, the Washington Post reported.
Hu has praised Jiang, saying, "We greatly appreciate his outstanding contribution to the party, the country and the people," reported the Australian Broadcasting Corp.
Jiang urged the party to follow Hu. "I hope that everyone will work hard and keep advancing under the leadership of the party Central Committee with Comrade Hu Jintao as general secretary," he said.
Jiang remains an influential behind-the-scenes figure for key policy decisions, particularly those with national reach. But the handover of authority to Hu, making him military chief as well as party leader and president, removes a sometimes awkward situation in which senior officers had complained of having two party lines of command, according to the Post.
Hu took over from Jiang as party leader in 2002 and replaced him as president of the country of 1.3 billion people the next year. But Jiang clung to his chairmanship of the 2.2 million-member military establishment. His term would have lasted another three years if he hadn't resigned.
It was unclear whether Jiang was pushed out or left voluntarily. His resignation letter, released Sunday, said he stepped down for the stability and development of the party and country.