AP -- North Korea's new leader vowed in 2009 to wage war if the country's enemies shot down its long-range rocket, footage aired on state television showed Sunday in the first official word of his role in military operations before his father's death.
The documentary is the second in a week seeking to highlight Kim Jong Un's experience in leading North Korea's 1.2 million-strong military and was aimed at showing that he was in charge of the armed forces long before his father, former leader Kim Jong Il, died of a heart attack last month.
The son, who is in his late 20s, has moved swiftly into the role of "supreme leader" of the people, the ruling Workers' Party and the military despite questions abroad about how easily he could assume power with only a few years of grooming behind him. Kim Jong Il, in contrast, had 20 years of training when his father, North Korea founder Kim Il Sung, died of a heart attack in 1994.
Where a North Korea under Kim Jong Un is headed is deemed crucial because the country is locked in a long-running standoff over its nuclear ambitions and is grappling with chronic food shortages. North Korea has tested two atomic devices and is believed to be working toward mounting a bomb on a missile capable of reaching the U.S.
After years of acrimony, Pyongyang and Washington had begun discussions about food aid and how to restart nuclear disarmament talks that were suspended when Kim died last month. The U.S. and North Korea fought on opposite sides of the 1950-53 Korean War and do not have formal diplomatic relations.
Sunday's footage -- shown on a day believed to be Kim Jong Un's birthday -- confirmed that he was being groomed as early as 2009 to succeed Kim Jong Il. The choice of Kim Jong Un as successor among the elder Kim's three known sons was not revealed publicly until state media reported in September 2010 that he had been made a four-star general and a vice chairman of the Central Military Commission of the Workers' Party.
The video showed Kim Jong Un shaking hands with officials at a satellite control centre after scientists launched a rocket in April 2009 that stoked regional tensions and earned North Korea international sanctions and condemnation.
"I had decided to wage a real war if the enemies shot down" the rocket, Kim Jong Un was quoted as saying. A voice-over described Kim Jong Il as saying his son was in charge of the military's anti-rocket interception operations at the time.
North Korea has said it successfully sent a satellite into orbit as part of a peaceful bid to develop its space program. U.S. and South Korean officials, however, said no satellite or other object reached orbit, and accused the North of using the launch to test its long-range missile technology.
At the time, Japan had threatened to shoot down any debris from the rocket if the launch went awry. U.S. lawmakers also urged their military to shoot the rocket down.
The video also showed Kim Jong Un navigating a tank, observing fighter jets and firing exercises, and posing for photographs with soldiers. He is shown seated in the tank's cockpit and speaking to officers with the hatch cover open. He later drove it on a snow-covered road as his father watched from a reviewing stand.
Both father and son wore heavy winter parkas. State TV did not say when the video was taken.
For two years, North Koreans were told that Kim Jong Un, who graduated from Kim Il Sung Military University, was a military genius, Pyongyang residents have told The Associated Press.
Sunday's documentary said Kim Jong Un had intensified military training, and showed fighter jets tearing through the skies, and soldiers jumping out of planes with parachutes and firing multiple-rocket launchers.
It cited Kim Jong Il as saying, "Our general resembles me. ... I sometimes admire his strong belief, resolve and gut."
Kim is also quoted as saying his son has "outstanding (military) strategies and is well-versed in military tactics. ... He is a man of many abilities and the genius among the geniuses."
Another documentary aired a week ago showed Kim Jong Un visiting a premier tank division with strong historical and family ties in the first solo inspection trip made after his father's death.
Since Kim Jong Il's death on Dec. 17, the process to install his son as leader has been quick, with top military and party officials wasting no time in pledging their loyalty to the third Kim to lead the nation of 24 million since it was founded in 1948.
Kim Jong Un, who was recently named supreme commander of the Korean People's Army, has pledged to uphold Kim Jong Il's "military first" policy.
He is believed to have turned 28 or 29 on Sunday, though his exact birth date has not been confirmed by the government. The birthdays of his father and grandfather are considered the nation's most important holidays, but Kim Jong Un's birthday has not been declared a national holiday.
AP Korea bureau chief Jean H. Lee contributed to this report. Follow her at twitter.com/newsjean.