He and his friend, Master sergeant Seo Dae-young (Jin Goo), are off-duty when they witness a young man stealing a motorcycle; they apprehend him using toy guns they had been using for a shooting game.

Mo-Yeon mistakenly assumes Si-jin is part of the thief's criminal gang after overhearing Dae-young address him as "Big Boss", which is his call sign.

Si-jin proves his identity with the help of army surgeon Yoon Myung-ju (Kim Ji-won), who turns out to be Mo-yeon's former rival from medical school.

Dae-young, on the other hand, faces a dilemma over whether to continue his relationship with Myung-ju or risk being forced out of the army for breaking fraternisation rules as he was not a commissioned officer.

Eight months later, Mo-yeon rebuffs the romantic advances of the hospital director and, as revenge, is assigned to lead a team of medical volunteers to Uruk against her will.

In Uruk, Si-jin and Mo-yeon reunite and both gain a deeper insight into one another's jobs as their respective teams endure an earthquake and an M3 virus (fictional disease described as being deadlier than ebola) outbreak, while also dealing with a local warlord who once fought alongside Si-jin in a joint mission between the South Korean and United States armed forces but now takes advantage of the corrupt government of Uruk to make money off human and arms trafficking.

She decides to commemorate the one-year mark of his passing by volunteering with a medical team sent to Albania, where Si-jin finds her toying with a pebble they had picked up from a beach.

[31] According to local reports by Newsis, lead actor Song Joong-ki was not the first choice of writers and directors for the hit South Korean series, as he was deemed too slender for the role of a heroic special forces officer.

[38][39] According to Greek and South Korean news portals and blogs, filming mainly took place in Zakynthos, Arachova, Lemnos, and Navagio.

[47] The director's cut, which feature a re-edited version of the last and 16th episode, as well as deleted scenes, a music video and behind-the-scenes footage, was released in the second half of the year.

[54] However, apart from Descendants of the Sun, none of the other pre-produced dramas thus far such as Moon Lovers: Scarlet Heart Ryeo, Uncontrollably Fond, and Hwarang: The Poet Warrior Youth have been successful.

[56] The announcement came about when lead actress Song Hye-kyo sued jewelry firm J.Estina for using her pictures for promotion though the contract ended in January.

[57] J.Estina said in a press release that it abided by the contract with production staff of Descendants of the Sun, which allowed it to use stills from the episodes as one of the main sponsors of the series.

[62] Descendants received immense popularity both locally, with a peaking rating of 40% in South Korea,[80] as well as internationally,[81] where it has been sold to 32 countries and translated into 32 different languages.

[85] The drama's success factors were attributed to its elaborate screenplay, beautiful love story and the co-production between South Korea and China.

"[87] Chinese Government mouthpiece People's Daily praised it as "an excellent advertisement for conscription" showcasing South Korea's "national spirit" and "communitarian culture".

[94] The drama's success helped boost Korea's economy; contributing in a rise of tourists, overseas sales of products (exports), and creating new jobs.

[11] The "Two Tone Lip Bar" lipstick that Song Hye-kyo wore in a scene on the show has broken sales records for Aritaum in South Korea with Laneige subsequently hosting its own Descendants of the Sun makeup event on its homepage.

[98] Laneige, Dal.Komm Coffee, KGC Cheong Kwan Jang Korean Red Ginseng, Subway and Hyundai all reported a surge in sales after exposure of their products in the drama.

[99][100] The popularity of the show has also led to KBS launching several merchandise of the drama, such as cookies, memory sticks, emoticons and commemorative medals, which were specially created and sold to fans.

[112] Navagio, one of the iconic locations where the "relationship between the lead characters blossom", experienced a surge in popularity among Chinese and Korean tourists.

[116] There is also a spike in the number of young men wanting to join South Korean special forces units for their mandatory military service.

The popularity of the show drew 8000 tourists from Vietnam, who signed up for tour packages to visit major sightseeing areas and filming locations of Descendants.

[126] Prior to the airing of the show, there was a debate on whether it's appropriate for Vietnamese to watch it given the alleged atrocities committed by Korean soldiers against civilians during the Vietnam War.

[133][134] In late 2016, Google Trends revealed that in 2016 most people in Sri Lanka searched for "Descendants of the Sun" rather than "Donald Trump" which stood in stark contrast to most of the world.

[142][143] Other critics argued that the drama promoted inaccurate perceptions of modern-day South Korean society, such as the existence of a cohesive military culture, and implicitly espoused nationalist and patriarchal values.

Tuổi Trẻ journalist Tran Quang Thi stated in a Facebook post that "During the Vietnam War, Korean troops spread terror in a number of regions in the country, not among the army, but among innocent civilians.