The historical drama "Six Flying Dragons" has already started filming but that doesn't mean you will see it this summer. The saeguk began filming four months ahead of its first airdate.

So far filming involves only the child actors who will pay the younger versions of Shin Se Kyung and Yoo Ah In's leading characters. But there's plenty of time since the drama does not air until October and the adult actors don't show up until the third and fourth episodes.

Shooting so far in advance is unusual as many dramas only begin filming about a month before their scheduled airdates. But the story has a lot of historical ground to cover. The drama focuses on the story of several important real-life historical figures and adds a few fictional ones.

The real-life figures include Prince Lee Bang Won, who later became King Taejong, and Jung Do Jeon, his advisor. Yoo Ah In plays Prince Lee Bang Won. The prince helped his father found the Joseon dynasty and thought that earned him the automatic succession. But he had to fight his brother princes to secure the throne. Once he acquired that throne, he wanted to maintain complete authority.

Kim Myung Min plays Jung Do Jeon, the prince's political rival, a man who hoped for a more democratic nation. Jung Do Jeon wanted a country ruled by ministers, while the prince wanted to retain absolute power.

Shin Se Kyung, who last appeared in "The Girl Who Sees Smells," plays Boon Yi, the woman that Lee Bang Won, later King Taejong, loves. But she is not the only woman in his life. Gong Seung Yeon, last seen in "Heard It Through The Grapevine" and "We Got Married," has been cast to play her romantic rival.

Byun Yo Han, who was last seen in "Ex Girlfriend's Club" and the film "Socialphobia," plays Ddang Sae, a warrior who guards Jung Do Jeon. He and the man he protects are in love with the same woman, played by Jung Yu Mi, last seen in "Maids."

Yoon Kyun Sang, who played Lee Jong Suk's older brother in "Pinocchio" and will romance Ha Ji Won in "The Time I Loved You," plays Moo Hyul, Yoo Ah In's bodyguard.

And last but not least Lee Cho Hee, who played Kim So Hyun's classmate in "Who Are You - School 2015" plays a singer.

Kim Young Hyun and Park Sang Yeon, the writers crafting the screenplay for "Six Flying Dragons" previously wrote the successful saeguk "Tree With Deep Roots." Director Shin Kyung Soo also worked on "Tree With Deep Roots." Shin Se Kyung also appeared in "Tree With Deep Roots." The new drama is a prequel to that one, as it features some of the same characters when they were young.