SEOUL, Nov. 20 (UPI) -- Kenneth Bae, the Korean-American missionary who endured 735 days as a political prisoner in North Korea, is now leading a renewed international effort to realize a unified Korean Peninsula.

Bae, 57, a naturalized U.S. citizen, was the longest-held American citizen in North Korea since the Korean War -- an experience he now views as a mission to become a "voice for the voiceless" North Korean people.

Bae's ordeal began in 2012 when he was arrested while leading his 18th "Love DPRK Tour" group. He was charged with "conspiracy to overthrow the state" and sentenced to 15 years of hard labor. He became the first U.S. citizen to be confined to a North Korean kyohwaso, or re-education camp.

"The ultimate charge was that I had tried to overthrow the North Korean regime through prayer and worship," Bae said in an interview. His unintentional mistake was bringing an external hard drive containing a documentary that showed the suffering of ordinary North Koreans, which became evidence for the regime's accusations.

Before his arrest, the "Love DPRK Tour" was focused less on proselytizing and more on cultural exchange and prayer for the land. Bae took some 300 people from 17 countries over two years to engage in activities like making kimchi, learning traditional dance and simply "walking the land" while praying for the North Korean people.