President Moon Jae-in became the first South Korean leader to give a speech to the North Korean public when he spoke at the Mass Games in Pyongyang on Wednesday evening.
In his seven-minute long speech, he said the two countries should “become one”, as they were before the war.
Mr Moon is on a three-day visit to Pyongyang where he signed a landmark agreement with Kim Jong-un.
The games are one of Pyongyang’s biggest propaganda events.
Tens of thousands of people take part in intricately choreographed dance and gymnastic displays, which tell stories of Korean history and myths. This year they are celebrating North Korea’s 70th anniversary.
Both leaders received a standing ovation from 150,000 thousand citizens when they entered the May Day Stadium in Pyongyang.
“I propose that we should completely end the past 70 years of hostility and take a big stride of peace to become one again,” said Mr Moon in his speech, which was broadcast live in South Korea though not in North Korea.
He also brought up the topic of denuclearisation during his speech, calling for nuclear weapons to be removed “permanently”.
Andray Abrahamian, a fellow at the Pacific Forum told the BBC: “It is unprecedented that he addressed he North Korean public.”
“The speech was clearly tailored to the North Korean audience.”
Mr Abrahamian adds that the mood at the stadium would have been “incredibly emotional”, saying that the “performances combined with Moon’s speech was designed to tug on the heartstrings of the public”.
“It really is an emotional appeal by Moon for support in North Korea. I’m sure now his popularity in the North will be unprecedented.”
Thousands of children participate in the Games, and several rights groups have criticised their involvement as forced child labour.
In a highly symbolic move, the Korean leaders made a visit to Mount Paektu to conclude the three-day summit.
The mountain holds a central place in Korean mythology and features in South Korea’s national anthem and various North Korean propaganda.