[12] Badreddine's appointment as the head of overseas operation was not supported by deputy general secretary of Hezbollah, Naim Qassem.

[18] Following the beginning of the Syrian Civil War in 2011 Badreddine went to Syria as one of the Hezbollah commanders to defend the government of Bashar al-Assad.

[23] In order to force the authorities to release Badreddine and others, Hezbollah members headed by Imad Mughniyeh kidnapped at least four Western citizens in Lebanon.

[4] In June 2011, Badreddine and other three people were indicted for charges related to the assassination of former Lebanese Prime Minister Rafiq Hariri by the Special Tribunal for Lebanon (STL).

[44][45] Badreddine and Talal Hamiyah were put on the list of Specially Designated Global Terrorists by the US Treasury Department on 13 September 2012 due to his alleged role as top military commander, replacing Mugniyah who died in 2008.

[47] On 13 May 2016, it was reported that Badreddine had been killed by an explosion near the Damascus International Airport, the cause and timing of which remained unclear.

[20][48] Al Manar TV announced Badreddin's death stating that he was the target in a huge blast near the airport and that other Hezbollah fighters were wounded.

The station added that the Hezbollah did not immediately point a finger at Israel and they would investigate whether the blast was from an airstrike, rocket attack or other cause.

[52] Then Hezbollah stated that an attack was launched by "Takfiri groups" and said: "Investigations have showed that the explosion, which targeted one of our bases near Damascus International Airport, and which led to the martyrdom of commander Mustafa Badreddine, was the result of artillery bombardment" carried out by Takfiri groups.

"[53][54] This claim is disputed by the Syrian Observatory for Human Rights, who said that no artillery fire had been heard in the area in the past three days and announced that "There is no truth about what have been published by Hezbollah about the assassination of its military commander in Syria 'Mustafa Bader' by rebel shells near the international airport of Damascus".

[56][57] It is felt extremely unlikely that the Syrian rebels would have had the information and weaponry as the Middle East Eye reported that "the nearest opposition artillery positions … were 20 kilometres away, and there are doubts that their shells could achieve pinpoint accuracy from that distance."

[6] The Saudi-owned Al Arabiya reported that Badreddine was killed by his former bodyguard, a man he trusted completely and one of Hezbollah's top operatives, Ibrahim Hussein Jazini[59] and bodyguard of Hassan Nasrallah, by order of Nasrallah and Iranian general Qasem Soleimani.