The assassin could not have picked a more critical time. His bullet killed perhaps the most courageous, most outspoken fighter for a compromise between Palestinians and Israelis the very day Palestine Liberation Organization chief Yasser Arafat defeated the latest and maybe the last chance for a peaceful resolution of the Palestinian problem.
Dr. Issam Sartawi, a Palestinian-born one-time Cleveland heart surgeon, carried a gun but knew that his people would not regain their rights on the battlefield but only at the negotiating table.
Dr. Sartawi kept his gun because he was aware that his many enemies - both within the ranks of the Palestinians and among Arabs in general - had long declared him a marked man.
Yet the gun he had long disavowed to restore his people's rights was also of no use when his opponents finally moved to kill him April 10 in the lobby of a hotel in Portugal.
Sartawi waged a lonely struggle for mutual recognition between Israelis and Palestinians of each other's rights.
Although conscious that he was in permanent danger, Sartawi refused to compromise on this principle which he held so sacred.
Many will see his death as a warning to Mr. Arafat not to permit current efforts to revive the Middle East peace process to get off the ground.
Last month friends of Sartawi warned him that his life was in imminent danger and that his death would serve as a message to Arafat. Sartawi chose to disregard the warning.
Supported by Arafat, he initiated a process aimed at drawing the PLO into the diplomatic mainstream - a process that would turn guerrillas into statesmen and politicians.
Based in Paris, Sartawi paved the way for acceptance of the PLO among prominent West European government and labor party leaders. He built a close and emotional relationship with Austrian Chancellor Bruno Kreisky who encouraged him in his increasingly close contacts with members of the Zionist left in Israel.
Despite repeated threats on his life, fierce denunciations by Arab and Palestinian radicals, and even occasional pressure from Arafat himself to loosen his ties to prominent Israeli doves, Sartawi refused to budge.
He was aware that despite his often violent disagreements with the PLO chairman over both Palestinian tactics and strategy Arafat would always do his best to protect him.
Sartawi's only official title was member of the Palestine National Council, the PLO's highest policymaking body. But in effect, Sartawi served as Arafat's personal emissary to both West Europe and the Israeli peace camp.
In July 1979 Arafat paid an official visit to Austria at a time at which a reportedly Syrian- and Iraqi-backed Palestinian dissident gunned down some of Arafat's closest associates.
In a private conversation with Chancellor Kreisky, Arafat - aware of the severe opposition among segments of both the Palestinian movement and the Arab world to his careful steps toward moderation - reportedly said, ''I had five friends; four of them are dead. The fifth is Sartawi.''
Three months later, the newly installed Kreisky peace prize was awarded in Vienna by Austrian President Rudolf Kirchschlager to Issam Sartawi and Arie Aliav, the former secretary general of the Israeli Labor Party. The prize was a tribute to their courage in maintaining a dialogue between them despite the heavy pressure exerted individually on both of them from within their constituencies.
The ceremony followed a night of agonizing phone calls between Vienna, Beirut , and Damascus. Enraged about this ''act of capitulation and treason,'' Syrian President Hafez al-Assad brought heavy pressure on Arafat to ensure that Sartawi would reject the prize. In response to Arafat's request not to attend the prize-awarding ceremony, Sartawi tendered his resignation to Arafat with the words: ''What value does my quest for peace have if I cannot stand on a public platform with my brother Arie Aliav?''
Sartawi's resignation was rejected by Arafat following the ceremony.
In an interview with Israel radio after Sartawi's death yesterday Arie Aliav said: ''He met me as a Zionist. I met him as a proud Palestinian. He lived in danger. I think he was one of the proudest and most courageous men I met in my life. He was a pioneer.''
Earlier Sartawi's execution was demanded by radical, pro-Syrian and pro-Iraqi Palestinian organizations during the 1977 Palestine National Council meeting for ''betraying the Palestinian cause'' by talking to Zionists, Israelis, and Jews. In a fierce speech to the council, Arafat came to his defense.
In February of last year, the Popular Front for the Liberation of Palestine again called for his death, publishing his picture as that of a marked man. Again Arafat intervened successfully to quash the danger.
But last month's warning to Sartawi implied that the danger came from circles too big even for Arafat to control - circles that threatened Arafat's own life if he allowed President Reagan to implement US Middle East peace proposals.
PLO military chief Abu Jihad told reporters in Amman April 10 that the PLO believed that Sartawi's assassin could be ''Abu Nidal, who we believe is serving Israeli interests or maybe other Arabs.'' When asked if this might mean the Syrians, he refused to comment.
Abu Nidal, a Palestinian dissident allegedly backed by both Syria and Iraq, issued a statement April 10, saying, ''We implemented the death sentence with Palestinian and Arab bullets on Issam Sartawi . . . the enemy of our people.''
Last year Abu Nidal claimed responsibility for the attempted assassination of Israel's ambassador in London, Shlomo Argov. The attempt on Mr. Argov's life served as the pretext for Israel's invasion of Lebanon.
Sartawi played a prominent role in documenting links between Syria and Abu Nidal, who is reported to have plotted to kill both former Egyptian President Anwar Sadat and PLO leader Arafat in the summer of 1981. These revelations also helped lead to the expulsion from Austria of the official PLO representative, Ghazi Hussein, a member of the Syrian-controlled Saiqa guerrilla organization.
Born almost 50 years ago in the now-Israeli town Acre, Sartawi had impeccable revolutionary credentials.
Shortly after the 1967 Arab-Israeli war, Sartawi established in Jordan his own guerrilla group. Two years later a prominent Israeli actress was crippled for life when his men attacked an Israeli airliner in Munich.
Sartawi's justification for the attack was a simple one: ''This was in memory of my brother,'' he said, who was killed during an Israeli attack in the Jordan valley.