From 03/1973 Syria was ruled by socialist secular Baath party and the Syrian Army led by Hafez al-Assad. The al-Assad family is Alawite and in order to strengthen their grip on power, as it is so common in the Middle East, all the key functions in the political party, the army and security services were in the hands of Alawites.
The Alawite minority keep to a particular interpretation of Islamic Shiaa. Many Sunnite scholars refer to the Alawites as an inferior agnostic sect. As a result a Sunnite violent Islamic underground, based on the Muslims Brotherhood,  carried out intensive bloody terror attacks all over Syria in the late 70s’ and the early 80s’ as an opposition to Alawite regime.
After the January 1979 Islamic Revolution in Iran, led by Ayatollah Khomeini Islamic motions were intensified all over the Muslim world including Syria and Sunnite terror attacks in Syria increased sharply.
On 02/02/1982 Islamists and other opposition activists proclaimed Hama a “liberated city” and urged Syrians to rise up against the “infidel” (meaning – Alawites). Brotherhood fighters swept the city of Baath supporters, breaking into the homes of government employees and suspected supporters of the regime and killed about 50 people.
The Syrian Baath Regime responded fast and surrounded the town of about 350.000 citizens with tanks, artillery and special units under the command of Rifaat al-Assad, the brother of the President Hafez al-Assad. The assault began with extensive shelling of the town. Before the attack, the Syrian government called for the city’s surrender and warned that anyone remaining in the city would be considered as a rebel. After a two-week battle, the town was securely in government hands again. The following several weeks witnessed torture and mass executions of suspected rebel sympathizers, killing many thousands, known as the “Hama  Massacre”.
According to Amnesty International estimation between 10,000 and 25,000 were killed in “Hama  Massacre”.

Summary

The Hama  Massacre in 03/1982 put an end to any Islamic terror activity in Syria for more than 20 years. Islamic militants who managed to flee Syria to Europe were granted, in most cases, political asylum.
Many of those asylum seekers became later pillars of Islamic terror cells in Europe related to Al Qaeda and caused major concern to European Security Services.

Rifaat al-Assad, the executer of Hama  Massacre, lived later many years in Spain and UK as a respected businessman and was never charged for committing any sort of War crimes against humanity.