After dozens of Palestinian civilians were killed following an Israeli airstrike in Rafah this week, the White House made clear: The incident did not cross the red line President Joe Biden has drawn when it comes to providing certain American weapons to Israel.

Where, exactly, that line rests remains somewhat elusive since Biden first confirmed to an interviewer in March that such a threshold exists.

Biden’s aides, acutely aware of previous presidents who drew red lines only to back away from any promised action when they were crossed, once dismissed talk about “red lines” as a media obsession.

“The whole issue of the red line, as you all define it, is something that you guys like; it’s almost become a bit of a national security parlor game,” Biden’s national security adviser Jake Sullivan told reporters in March, after the president suggested for the first time that an invasion of Rafah would prompt him to rethink some aspects of his policy.

At the very least, however, Biden’s own comments since then suggest there are actions Israel could take that would trigger a new approach from the United States. He has told Prime Minister Benjamin Netanyahu as much during telephone calls and conveyed his stance publicly in an interview with CNN.

But he has remained vague about how he will quantify such a decision, leading to frustrations and a degree of confusion about his stance. Many Democrats, along with foreign leaders who the US counts as allies, say Israel’s actions clearly cross a red line – if not Biden’s, then their own and those of international law.

“President Biden rightly drew a red line for US support on a full-scale invasion of Rafah, but I think it’s unclear to the public the difference between what we’re seeing now and what would be crossing that red line,” California Rep. Sara Jacobs told Secretary of State Antony Blinken at a House Foreign Affairs Committee hearing last week – before the Israeli strike that resulted in the deaths of 45 civilians in a displacement camp.

From the onset of the conflict, prompted by Hamas’ attack on Israel that killed 1,200 people, Biden and his team have been highly wary of setting parameters on Israel’s response.

“I’m not standing up here to draw red lines,” Sullivan told reporters on October 10 when asked about the parameters of Israel’s operation and how far US support would stretch.

“What I’m standing up here to say is that in its hour of need, as Israel embarks on an operation to try to protect its country, protect the Jewish state of Israel, and to go after the threats that it faces – and also working closely with them hand in hand to try to secure the release and recovery of American and other hostages, we will do all of that,” he added.

The message from Biden and his top advisers in the weeks and months that followed was that American support would not wane, even as the president warned Netanyahu about the need to protect civilians and calibrate his military operations.

The first signs of a red line

It was on March 9 – as Israel was making plans to enter the southern Gaza city of Rafah, where more than a million civilians were sheltering – that Biden first confirmed a “red line” existed at all.

“What is your red line with Prime Minister Netanyahu? Do you have a red line? For instance, would invasion of Rafah, would you have urged him not to do? Would that be a red line?” MSNBC’s Jonathan Capehart asked during an interview.

“It is a red line, but I’m never going to leave Israel,” the president responded. “The defense of Israel is still critical, so there’s no red line I’m going to cut off all weapons so they don’t have the Iron Dome to protect them.”

“But there’s red lines that if he crosses…” Biden went on, trailing off before finishing his thought. “Cannot have 30,000 more Palestinians dead.”

The statement triggered rounds of questions at the White House. His answer, with its incomplete sentences, did not state what might constitute a violation of the red line or what his response would be.

“The president didn’t make any declarations or pronouncements or announcements,” Sullivan told reporters in the following days. “The red line came up in a question. He was responding to that question. I think he gave a full answer to it. I think it’s worth going back and reading his full answer to that question.”

The next week, his answer was similar.

“I went over the red line issue, which I know is the obsession of this group, last week. I’ve got nothing more to say on that front,” Sullivan said on March 18. “As you know, particularly for me, I think that’s something that is posed in your questions; it’s not stated as a declaration of our policy.  And we’ve made that clear.”

The next week, the same.

“I’m just not going to get into the parlor game of what tripwire would be in place or what we would consider a tripwire in order to change the way we’re supporting Israel in the field,” he said.

Whether Biden drew a red line or not, his counterpart in Israel found reason to dismiss the president’s comments.

“You know, I have a red line. You know what the red line is? That October 7 doesn’t happen again,” Netanyahu said, an early indication that Biden’s entreaties to avoid a major operation in Rafah were not being well-received in Israel.

An unclear limit is set

Indeed, in the weeks that followed, the rift that had been opening between Biden and Netanyahu widened dramatically.

American officials continued watching with concern as Israel made plans for going after Hamas in Rafah. Without a credible plan for protecting the civilians there, US officials warned, a humanitarian disaster would unfold.

Such a plan didn’t materialize, and Biden began considering steps that might limit what weapons the US provides Israel — a move he’d long been averse to taking.

By May 8, Biden had already paused one shipment of heavy bombs out of fear they could be used in densely populated areas like Rafah. Across the US, protests had erupted on college campuses and elsewhere calling for an end to the war. And some Democrats, including close Biden allies, began calling for conditioning US aid.

Sitting down with CNN’s Erin Burnett, Biden for the first time said he was prepared to withhold certain types of weapons should Israel move on Rafah.

“I made it clear that if they go into Rafah – they haven’t gone in Rafah yet – if they go into Rafah, I’m not supplying the weapons that have been used historically to deal with Rafah, to deal with the cities, that deal with that problem,” he said. “We’re going to continue to make sure Israel is secure in terms of Iron Dome and their ability to respond to attacks that came out of the Middle East recently. But it’s, it’s just wrong.”

It was the clearest the president had been on when and how he might be forced to scale back his until-then limitless support. Behind the scenes, American officials said Israel was well aware of the president’s thinking.

But even then, his definition of “go into Rafah” remained indistinct.

Asked a few days later about the president’s comments, Blinken insisted on NBC’s “Meet the Press” that his boss had not, in fact, drawn a red line.

“Look, we don’t talk about red lines when it comes to Israel,” he said, adding later: “What the president said is that if Israel goes in with a major military operation in Rafah, in that case, there are certain systems that we will not provide to Israel that would aid that effort.”

White House avoids defining Biden’s threshold

White House aides went on to insist that a “major military operation” would be obvious should it unfold, even as they stopped short of offering qualitative criteria.

“We’ll make our own judgment on that as we see things unfolding, and it will be based on a totality of factors. It’s not a mathematical formula or a mechanical determination,” Sullivan said at the White House on May 13. “It’s something we will judge based on what we see. And the president will then make his determinations. We have not seen that happen yet.”

The next week, his answer expanded somewhat.

“What we’re going to be looking at is whether there is a lot of death and destruction from this operation or if it is more precise and proportional. And we will see that unfold,” he said on May 22.

Four days later, at least 45 people were killed and more than 200 others injured after a fire broke out following an Israeli military strike on the outskirts of Rafah, most of them women and children, according to the Gaza Health Ministry and Palestinian medics.

Footage obtained by CNN showed swathes of the camp in Rafah in flames, with scores of men, women and children frantically trying to find cover from the nighttime assault. Burned bodies, including those of children, could be seen being pulled by rescuers from the wreckage.

A CNN analysis of video from the scene and a review by explosive weapons experts found munitions made in the United States were used in the deadly strike.

The death and destruction were not in dispute, and the White House called the images “heartbreaking.”

“The word tragic doesn’t even begin to describe” the situation, Vice President Kamala Harris said.

Yet the episode did not meet Biden’s bar for stopping certain weapons shipments.

“We have not seen them go in with large units and large numbers of troops in columns and formations in some sort of coordinated maneuver against multiple targets on the ground,” said John Kirby, a White House national security spokesman.

A major ground invasion, Kirby said, would be obvious should it begin: “Lots of units of tens of thousands of troops or thousands of troops moving in a coordinated set of maneuvers against a wide variety of targets on the ground in a massive way. That’s a major ground operation. Pretty simple.”

One senior administration official said the strike on the displacement camp rendered the discussion moot, believing Israel will launch attacks on Rafah that are precise enough to placate Biden but not enough to mitigate the dangers to civilians.

“They are trying to do it in a way that allows the administration to say it’s below the line. But the net effect will be the same,” the senior administration official said.