Kim hobnobbed with top Chinese officials, including President Hu Jintao, toured factories and paid a nostalgic trip down Kim family memory lane, according to Chinese and North Korean state media -- possibly, rumor had it, accompanied by the son many believe is being groomed to succeed him as North Korea's next leader.
There was no sign of Kim Jong Un, the 20-something son said to be in his favor, and there was no mention of him in either nation's dispatches about the five-day trip that was shrouded in typical secrecy.
Still, signs that the North Korean regime is laying the groundwork for a succession movement abounded in the 68-year-old Kim's pointedly patriotic and strategic trip by train through northeastern China.
China remains North Korea's chief ally and benefactor, supplier of troops when the Korean War broke out 60 years ago and its main source of aid to this day. Beijing's continued good will is crucial for North Korea since its ailing economy is unable to provide enough food for its people. China provides food assistance and nearly all of North Korea's oil, and much of Pyongyang's trade, passes through China.
China is also the place where North Korea founder Kim Il Sung, father of the current leader, sowed his revolutionary roots as a budding guerrilla fighter when his family fled the Japanese occupation of Korea in the 1920s.
The trip -- just weeks after the 60th anniversary of the Korean War and during the 100th anniversary of Japan's annexation of Korea -- served to both solidify North Korea's ties with its most important ally and to emphasize the Kim family's patriotic lineage.
It also came as a surprise to those who expected him to be in Pyongyang, courting Jimmy Carter during the former U.S. president's own surprise trip to the communist capital last week.
North Korea has been building toward pivotal celebrations in 2012 to mark the 100th year of Kim Il Sung's birth, an occasion that would have been a key time for a regime change. However, time may be running out: Kim reportedly suffered a stroke in 2008, and is noticeably grayer and thinner than in the past.
The fact that Kim, who never flies and rarely travels abroad, was making a second trip to China in four months, gave the trip a sense of unprecedented urgency.
"His purpose is to increase economic and diplomatic assistance from China for his succession process, which is more urgent than before," said Shi Yinhong, a professor of international relations at Renmin University in Beijing. "This is the center of his concern."
Shi said the purpose of Kim's visit was to drum up support from China for the leadership succession, a process that Beijing also wants to see go smoothly. Analysts note that the trip comes just days before North Korea is to hold a Workers' Party congress next month -- the biggest political convention in 30 years.
The last major convention was in 1980, when Kim Jong Il was officially named to a senior Workers' Party post, and many believe the son similarly may be granted a key party position.
"With the party convention ahead, North Korea was trying to show its people economic and political stability through North Korean-Chinese cooperation, and to use the convention to make steady progress on succession," said Kim Yong-hyun, an expert on North Korean affairs at Seoul's Dongguk University.
It probably didn't hurt, either, to snub the ex-leader of the nation's longtime foe, the United States. Pyongyang remains locked in a standoff with Washington over its nuclear weapons program and the March sinking of a South Korean warship, a deadly incident the U.S. and South Korea consider a violation of the armistice signed in 1953. North Korea denies involvement.
In their meeting Friday in the city of Changchun, Kim and Hu discussed the nuclear disarmament talks that North Korea walked away from last year, with Kim telling the Chinese president Pyongyang hopes for an early resumption of the negotiations, China's state-run Xinhua News Agency said.
"With the international situation remaining complicated, it is our important historical mission to hand over to the rising generation the baton of the traditional friendship passed over by the revolutionary forefathers of the two countries," Kim said at their banquet, according to the North's official Korean Central News Agency.
Kim was shown embracing Hu in footage aired by China Central Television.
"The North Koreans wanted to show that they want to resolve the nuclear issue through North Korean-Chinese relations," analyst Kim Yong-hyun said.
He said it wasn't an outright snub but a strategic move to get Washington to act. "By getting closer with China, or at least making it seem like relations are strong, North Korea is indirectly trying to get the U.S. to be more aggressive and involved."
Other stops to factories and farms in Jilin, Changchun and Harbin, all former centers of heavy industry that have tried to remake themselves under free-market competition, were economic in focus. Kim also visited the construction site for a Catholic Church, KCNA said.
"We were deeply impressed and greatly encouraged to see for ourselves the resourceful and hardworking Chinese people," Kim Jong Il said in a message to Hu published Monday by KCNA.
But it was Kim's tour of sites highlighting the "footprints of revolution" that seemed to affect the aging leader most.
His first stop: Jilin Yuwen Middle School, which his father attended in the 1920s, and where Kim Il Sung is said to have nurtured his anti-Japanese fervor.
Seeing a chair and table his father used 80 years ago, "Kim Jong Il was overcome with deep emotion," KCNA said.
"I think he is probably bringing his son to visit the middle school that Kim Il Sung attended, and to visit the revolutionary site where he fought against Japan," said Cui Yingjiu, a retired professor of Korean literature at China's Peking University and former classmate of Kim's.
North Korea routinely highlights the Kim family patriotism when trying to shore up communism's first dynastic succession, analysts said.