In this file photo released by the Korean Central News Agency in 2019 December, North Korean leader Kim Jong-un rides a white horse up a snow-covered Mount Paektu. Yonhap

Many North Korea watchers were doubtful when Kim Jong-un, then 27, took over the Hermit Kingdom in December 2011 following the sudden death of his father, Kim Jong-il.

A decade later, apparently, few question Kim's grip on power, despite a host of challenges, such as its moribund economy, amid a wide web of sanctions led by the U.N. and the U.S. against his regime.

Through the past 10 years, Kim has effectively established his own leadership style using an extensive range of strategies, from building an image of a figure who cares about the lives of the people to the brutal killings of his own uncle and brother, outside watchers say.

Kim formally rose to power on Dec. 30, 2011, with the North's ruling Workers' Party announcing he "assumed the supreme commandership of the Korean People's Army." It was just 13 days after Kim Jong-il died of a heart attack.

Months later in April 2012, the party named him its "first secretary."

Efforts to groom the crown prince as the North's next leader began years earlier, but the 27-year-old still appeared to lack the political experience and close aides necessary to support a smooth father-to-son power transition and help solidify his leadership.

Kim Jong-il, for one, prepared for two decades to take over the helm of the North from his father and national founder, Kim Il-sung, in 1994, as the succession process began in 1974.

One of the first things Kim did upon taking the throne was to restore the party system to keep the military ― which had developed immense power under his father's military-first policy ― in check and give authority to the relatively young leader's decision-making process.

In 2016, North Korea held a four-day party congress, the first of its kind in 36 years, and announced the "byongjin" policy of simultaneously pursuing nuclear weapons and economic development.

In January this year, the North held another party congress and endorsed Kim as the "general secretary," a title previously held by his father.