He participated in scientific research at the level of the city of Moscow, and presented a thesis entitled "Calculating the protective thickness of tunnel facilities in the Syrian Arab country when affected by conventional weapons and weapons of mass destruction and in all types of soil", which is a computer program in the Pascal programming language.

However, after the outbreak of violent protests across the country in 2011, Hussein announced his defection from the army on June 10, 2011, during the campaign on the city of Jisr al-Shughour, along with a number of his comrades, justifying this by saying that it was due to “the killing of unarmed civilians by the regime’s forces.”[6] Hussein Harmoush later said in a more detailed statement that he was sent to several cities during the protests, including Saqba in the Damascus countryside and Jisr al-Shughour in Idlib Governorate, and when the army began its second invasion on Sunday, June 5, he and a number of his comrades planted mines and placed obstacles in the army's path to slow its advance, but he had not yet defected at that time.

[13][14] A third account says that he was part of a deal between the Syrian and Turkish governments in which Turkey exchanged Al-Muqaddam for nine members of the Kurdistan Workers’ Party that it wanted.

[15] The fourth account says that he did not leave Syria at all, but was arrested inside it during the army's invasion of border towns in northern Idlib Governorate.

[12] After Hussein Harmoush was arrested, the Syrian Army began an invasion of the village of Iblin in Jabal al-Zawiya, where the lieutenant colonel was born and where most of his family lives.

[13] On the morning of Thursday, September 8, the army entered the village with a tank, seven armored vehicles, and dozens of cars carrying security personnel.

Hussein Harmoush's brother, “Mohammed,” was working at the time to help defectors from the army escape to Turkey, so there were 15 soldiers and two officers in his home when the invasion began.

[17] Shortly after these events, the Syrian SANA news agency said on the evening of Thursday, September 15, that it would soon broadcast Hussein al-Harmoush's “confessions” about him and his movement.