"It is our view that decapitation of the terrorist infrastructure is one means among the strategies in the war against terror," Yaalon said.
He said also that the 22 March killing of the revered Palestinian figure by Israeli forces in Gaza City might, at least temporarily, strengthen Hamas.
"The strike on Yassin is a significant blow to the Hamas terror organization. Maybe, in the short run, such an act may strengthen the emotions and the motivation of Hamas," Yaalon said.
Events later in the day bore him out. Two prominent Hamas figures known for tough talk against Israel claimed the group's top leadership. They are Abdel Aziz Rantisi and Khaled Mashal.
At a public rally in Gaza City, Rantisi said that he is stepping up to assume leadership of Hamas for the Gaza Strip. Rantisi said that Hamas will unify and persevere.
"We have to unify in the trench of resistance. We will not surrender and we shouldn't surrender in front of the Israeli terror," Rantisi said.
The goals of Hamas, he added, will be the same as they were under Yassin's leadership.
"Sheikh Ahmed Yassin is our symbol and we will continue on the same policy of Sheikh Ahmed Yassin and we will carry all the goals that Sheikh Ahmed Yassin believed in," Rantisi said.
Rantisi is a 54-year-old physician who has said that he opposes any truce with Israel. He spent seven years in Israeli prisons, and in 1992 was sent into exile in Lebanon along with several hundred other Hamas members.
Last June, he suffered injuries when his car was hit by an Israeli missile on a Gaza City street. Afterward, he appeared undaunted, saying Hamas would never give up the fight for Palestinian liberation.
"We must remember that the Palestinian people, the Arab world, and the Muslim world must be victorious. For our pride, we must fight those who came to hurt us inside our homes. At Hamas, we will not drop our weapons, even if all leaders are assassinated. We will not drop our weapons. This is the only option for the Palestinian people. It is the only hope in order to liberate our land and end the slavery of our people from occupation. Martyrdom and jihad operations will continue, God willing," Rantisi said.
In his comments yesterday, Rantisi said that Khaled Mashal, a physics teacher in his late 40s who directs Hamas's political bureau from Damascus, will be what he called the group's "first head," its world leader. Rantisi said he will answer to Mashal's lead.
In 1997, Mashal survived an attempt by Israel's Mossad intelligence agents to murder him with poison darts.
Both men -- Rantisi in particular -- are opposed to compromise with Israel.
Other major Hamas figures are also in line to assume stronger leadership positions. One is Mahmoud Zahar, a 53-year-old political leader who also served as Yassin's personal physician.
Zahar might have been considered a rival of Rantisi and Mashal, but at yesterday's rally, he shook Rantisi's hand in an evident acceptance of the new leadership.
Others include Ismail Hanieh, a top aide to Yassin, and Moussa Abu Marzoon, Mashal's deputy in the political bureau.
Yassin, who established Hamas in 1987 and remained its most central authority, seemed to defy Israeli threats on 21 March in what may have been his last television interview, broadcast by Arab television station Al-Arabiyah.
"The Israeli threat to eliminate Hamas leaders and leaders from other factions is not a new threat but an old one used repeatedly. Every time there is a martyrdom operation [suicide attack] or an operation which hurts the enemy, Israel begins to threaten [that it will respond]," Yassin said.
The next day he was dead, targeted in an Israeli military operation that drew widespread international condemnation. After his death and despite the international reaction, Israel renewed its threats against Hamas's leadership.
Israeli Foreign Minister Silvan Shalom sad yesterday at a news conference in Washington that no Palestinian militant leader can consider himself safe from Israeli reprisal.
"We would like to believe that [the killing of Yassin] is a very strong message and a very strong signal to all the extremists that, from now on, they don't have immunity anymore," Shalom said.
The United States was muted in its reaction to the Israeli action. A White House spokesperson urged both sides to exercise restraint, but stopped short of condemning the attack.
Hamas spokesmen at first said they held the United States partly responsible for the Israeli action. But at a 23 March rally, speakers directed their anger and threats only against Israel.