The Israel Defense Forces opened an investigation into an airstrike last night that killed at least 45 Palestinians at a tent camp for displaced people in Rafah, Axios' Barak Ravid reports.

• Israeli Prime Minister Benjamin Netanyahu called the civilian deaths "a tragic mistake."

Behind the scenes: The White House is now assessing whether the Israeli airstrike violated President Biden's "red line," two U.S. officials told Axios.

• Biden threatened earlier this month to suspend the delivery of some U.S.-made offensive weapons if Israel entered population centers in Rafah, the city in southern Gaza viewed as Hamas' last stronghold.
• U.S. officials later explained that a humanitarian crisis, as a result of the mass displacement of civilians from Rafah, could also constitute a violation of Biden's red line.

What they're saying: "The devastating images following the IDF strike in Rafah last night that killed dozens of innocent Palestinians are heartbreaking," a White House National Security Council spokesperson told Axios.

• "Israel has a right to go after Hamas ... but as we've been clear, Israel must take every precaution possible to protect civilians," the spokesperson said.

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Military labs are making strides toward identifying the tens of thousands of soldiers killed in World War II and unaccounted for in the decades since, AP's Josh Funk reports.

• Why it matters: Generations of American families have been unable to honor their lost relatives with proper burials. The work of the Defense POW/MIA Accounting Agency is helping change that.

🔬 Zoom in: Forensic anthropologists, medical examiners and historians at a pair of federal labs in Nebraska and Hawaii are piecing together identities with the help of advances in DNA and X-ray technology.

• The labs have a goal of 200 identifications annually, with the number of success stories steadily rising since work began at Offutt Air Force Base near Omaha in 2013.
• About 82,000 soldiers from World War II and other conflicts remain unaccounted for. Experts believe about half of those remains are recoverable.

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A traveling memorial flag for the Global War on Terrorism is displayed today near the Lincoln Memorial on the National Mall.

Go deeper: The meaning behind Memorial Day.

At least 20 professional women's sports teams will play their inaugural season in 2024, Axios' Ashley Mahoney and Simran Parwani report.

• Why it matters: It's a historic time for viewership and engagement in women's sports. Investors are taking notice.

Between the lines: Women's sports fans have higher engagement rates than men's sports fans, according to research by PricewaterhouseCoopers.

• Keep reading.