Mamdouh Saydam (Abu Sabri) was born in 1940, in the town of ‘Aqir in the Ramla governorate. 

In 1948, Abu Sabri and his family were displaced to Al Majdal, then to Gaza, where the family finally settled in the Nuseirat Refugee Camp. 

Abu Sabri completed his elementary and preparatory school education at Nuseirat Preparatory School of the United Nations Relief and Works Agency (UNRWA). He then attended at the Khaled Bin al Walid Secondary School. 

In 1956, the Israeli occupying authorities tortured Abu Sabri in front of his father, who was also detained with him, in a prison in the Gaza Strip. The prison was established by the Israeli authorities following their 1956 occupation of the Gaza Strip.  

After his release, Abu Sabri entered the Alexandria University and chaired the Palestinian Students’

Association. He obtained a B.A. in geography from the Faculty of Arts in 1963. 

After he graduated in 1963, Abu Sabri worked in Algeria as a teacher in the city of Al Buleida for a short time. After he resigned, Abu Sabri joined Fatah and worked at the PLO Palestine Office in Algiers, managing the cultural and educational affairs of Palestinian students. 

Abu Sabri completed military training at the Algerian Cherchell Military Academy. Later, he pursued higher education in military sciences at the Naan Kapen College in the People’s Republic of China.  
He took several military training courses and supervised the graduation of Palestinian officers from military academies in Algeria. In 1964, Abu Sabri participated in the military struggle on the land of Palestine with his revolutionary colleagues. He had earlier resigned from his post at the PLO Palestine Office. 

In February 1966, Abu Sabri, Yasser Arafat and other Fatah fighters were arrested in Damascus after Yousef ‘Urabi, a Palestinian member of the Baath Party and officer of the Syrian army, was killed.

Following the Israeli occupation of the West Bank in 1967, Fatah assigned Abu Sabri to command the Jenin area.  He, therefore, accessed the occupied Palestinian territory and participated in many battles against the Israeli occupying forces, most notably the Beit Furik battle of the 7th of December 1967, in which the Israeli forces sustained major losses. 

Later, Abu Sabri was put in charge of Fatah’s work in Jordan, responsible for communications with the military command of the Jordanian army. To present and promote the question of Palestine, Abu Sabri chaired and participated in several Palestinian Revolution delegations to China and the Soviet Union, among other countries. 

On the 21st of March 1968, Abu Sabri was among the first to participate in the battle of Al-Karamah. He also participated in several battles and operations against the Israeli occupying forces, including at Al ‘Arqoub and Ghor Al-Safi. He was elected Deputy General Commander for Operations of the Storm Forces. 

During the battles of September 1970, Abu Sabri was assigned to command the Palestinian Revolution Forces in the Jarash- ‘Ajlun area of Jordan.

In early 1971, Abu Sabri was stricken with an incurable disease and died on the 24th of July 1971. He was buried in the Al-Shuhada cemetery in the Al-Yarmuk refugee camp in Damascus.