He originally studied engineering in the late 1950-60s where he organized an Islamist slate, Shabab al Aqsa, to compete in student elections.
He spent time as a refugee in Yarmouk camp, near Damascus,[4] Al Hassan returned to Gaza in 1995 and began to act as the head of Foreign Relations in Fatah and a political adviser to Arafat.
[4] He served as regional head in Jordan briefly in early 1970, then as Salah Khalaf's deputy in Rasd, along with being a central committee leader during this time period.
He was critical of the leadership's stance towards Iraq after August 1991, and at Oslo, but returned to Gaza Strip in November 1995, and became the chief political adviser to Arafat as well as PLO-CC member & head of the Palestinian National Council foreign relations committee.
Al Hassan was head of Fatah's Bureau of Mobilisation and Organisation and (maktab at-ta`bia wat-tandhim) until April 2007, when he was replaced in that role by Ahmed Qurei.