Israel, he said, has defined four types of weapons whose transfer to militant groups would not be tolerated: advanced air defense systems, ballistic missiles, sophisticated shore-to-sea missiles and chemical weapons.

In accordance with this policy, Yadlin said, “any time Israel will have reliable intelligence that this is going to be transferred from Syria to Lebanon, it will act,” although specific decisions to strike would be subject to assessments of the military value of the attack, the risk of escalation and the positions of foreign powers.

“As the Syrian army becomes weaker and Hezbollah grows more isolated because of the loss of its Syrian patron, it makes sense that this will continue,” Yadlin said, adding that Israeli responses would be weighed each time and “not happen automatically.”

The real dilemma facing Israeli officials, Yadlin said, is not whether to attack, but whether inaction would mean a greater threat later.