When President-elect Joe Biden finally starts getting intelligence briefings, he may want to pay special attention to Israel’s successful operation against Abu Muhammad al-Masri, al-Qaida’s second in command.

The significance of that operation, which took place in August and saw al-Masri shot dead in the street, is its location: Iran.

According to the center-left conventional wisdom, this sort of thing should be impossible. While many analysts acknowledge that senior al-Qaida leaders fled to Iran after the fall of the Taliban in Afghanistan, they have insisted that there was no significant relationship between the Shiite majority regime in Tehran and the Sunni-jihadist terrorist group.

In fact, al-Qaida’s No. 2, who was wanted by the FBI for his role in planning the 1998 attacks on U.S. embassies in Africa, was living freely in an Iranian suburb. It should be obvious by now that Iran is willing to cooperate with al-Qaida when their interests converge.

This came to the public’s attention in 2017, after the CIA released a batch of documents recovered at the compound of Osama bin Laden in Pakistan. One of those documents is a 19-page memo laying out the quarter-century history of al-Qaida’s relationship with Iran. It says Iranian intelligence offered al-Qaida money, arms and training and facilitated the travel of some operatives, while providing safe haven for others.

All of this is relevant to Biden as he navigates how to achieve his own stated goal of rejoining the Iran nuclear bargain from which the U.S. withdrew in 2018. If Biden proceeds with his current plan of lifting nuclear sanctions on Iran in exchange for its return to compliance with the nuclear agreement, what will his administration do to deter Iran from supporting terrorism? The current administration has sanctioned Iran’s central bank and military for sponsoring terror. Will Biden keep those sanctions in place?

Another question for Biden is whether he will encourage Israel to continue its daring intelligence operations inside Iran. When Biden was vice president, the U.S. discouraged Israel from assassinating Iranian nuclear scientists, particularly as it conducted the diplomacy that led to the 2015 nuclear deal.

The August killing of al-Masri occurred during a summer in which a number of strategic sites inside Iran exploded as a result of what appears to be Israeli sabotage.

Biden and his team will have to decide whether constraining Israel helps or hinders the goal of containing Iran.

Eli Lake is a Bloomberg Opinion columnist covering national security and foreign policy.