By 1926 Yun had become an independence activist, starting evening classes in his home town to help educate people from rural communities about the issues.

After successfully organizing a well-attended rural cultural festival in which he performed a sketch entitled "The Rabbit and the Fox", he came to the attention of the Tokubetsu Kōtō Keisatsu, the Japanese Secret police in Korea tasked with investigating people and political groups that might threaten the Empire of Japan.

He travelled alone through Dalian, south of the Liaodong Peninsula, to Qingdao, Shandong Province where he worked at a factory run by Park Jin, a Korean businessman, to save money.

After more than a month of resistance, the Chinese forces gradually lost ground and eventually abandoned their positions in Jiangwan and Zhabei, retreating across the entire front.

However, the Japanese, wary of potential threats, declared that "no Chinese would be allowed to attend the victory celebration," making it difficult to act.

He contacted Ahn Chang-ho, the Minister of Internal Affairs of the Provisional Government, with whom he had a close relationship, and proposed the plan, offering a sum of 40,000 yuan for funding.

Ahn Chang-ho subsequently met with Kim Gu, the Minister of Police of the Provisional Government of the Republic of Korea at the time.

After accepting the mission, Kim Gu, learning from the failure of Lee Bong-chang's attempt to assassinate Emperor Hirohito during the Sakuradamon Incident, meticulously prepared the explosives.

On 29 April 1932, Yun took a bomb disguised as a water bottle to a celebration arranged by the Imperial Japanese Army (IJA) in honor of Emperor Hirohito's birthday at Hongkou Park.

The bomb killed the government minister for Japanese residents in Shanghai, Kawabata Teiji [ja], and mortally wounded General Yoshinori Shirakawa, who died of his injuries on 26 May 1932.

[10][11][12] However the future South Korean president, Syngman Rhee, disapproved of the incident and Kim Gu's strategy of assassinations as a means to achieve independence because the Japanese could use such attacks to justify their oppression in Korea.

[13][14][15] On 1 March 1962, the South Korean government posthumously bestowed on him the Republic of Korea Cordon (the highest honor) of the Order of Merit for National Foundation.

There is also a memorial hall called the Plum Pavilion in Lu Xun Park, Shanghai where the bomb throwing incident happened.

[18] In Kanazawa, Ishikawa, Japan, a monument was built on the site where Yun Bong-gil was buried after being executed by the Imperial Japanese Army.

In 2007, Anders Karlsson, a visiting Swedish scholar from SOAS, University of London, compared Yun Bong-gil and Kim Gu to terrorists in his lecture on Korean history.

[20] In 2013, Tessa Morris-Suzuki, an English historian and professor at Australian National University, concurred with Karlsson's explanation and wrote in her academic article, "If we accept the literal dictionary definition of the term terrorists as partisan, member of a resistance organization or guerrilla force using acts of violence then Yoo was self-evidently a terrorist.