President Obama said that the Libya war and its aftermath were the “worst mistake” of his presidency, highlighting the highs and lows of his administration in a candid interview, BBC News is reporting.

Specifically, Obama admits that his administration failed to properly prepare for the aftermath of Libya’s civil war, which ultimately led to warring factions vying for control of the country, leading to tens of thousands of casualties.

Back in February, 2011, protests erupted in Libya, and rebels aligned themselves into a militia groups aimed at ousting dictator Muammar Gaddafi.

As pro-government and rebel forces battled for control of Libya, the Obama administration — backed by the U.N. — carried out targeted airstrikes designed to protect civilians.

In October, 2011, Gaddafi was killed — but that hardly spelled the end of the strife in Libya. Over the ensuing months, rival factions vied for control of the North African nation.

In September, 2012, the U.S. Ambassador to Libya was killed, along with three other Americans, by Islamist militias targeting the U.S. Embassy in Benghazi. Current Democratic front-runner Hillary Clinton was Secretary of State at the time. To this day, Clinton’s role in the Benghazi attacks continues to haunt her campaign.

As of this writing, Libya is still in a state of civil war, and remains without a functional government. The U.N. announced a new interim government in January, 2015, but that government has yet to take control. Parts of the country are controlled by ISIS, and Libya has been known to act as a “jumping off” point for would-be jihadists hoping to join up with fighters in Iraq and Syria.

The debacle in Libya even led Obama to publicly call out his colleagues — specifically British Prime Minister David Cameron, whom Obama called “distracted.” The public rebuke was a rare move for a sitting U.S. president, and reportedly angered some within the Cameron government.

In a candid interview with the Atlantic, Obama admitted that his Libya policy has been a failure.

“So we actually executed this plan as well as I could have expected: We got a UN mandate, we built a coalition, it cost us $1 billion—which, when it comes to military operations, is very cheap. We averted large-scale civilian casualties, we prevented what almost surely would have been a prolonged and bloody civil conflict. And despite all that, Libya is a mess.”

In addition to opening up about his administration’s failures in Libya, Obama also spoke candidly to Fox News about some other benchmarks of his administration.

As for what Obama believes is the greatest accomplishment of his administration, Obama said it was “saving the economy from the great depression.”

Obama said his best day in office was when the Affordable Care Act was passed. His worst day, he says, was when learned of the Sandy Hook shooting.

A makeshift memorial to the victims of the Sandy Hook shooting. [Photo by John Moore/Getty Images]

Obama has spoken candidly before about his regrets. In a July, 2015, BBC News interview, Obama mentioned mentioned his failure to pass “common sense” gun regulations as one of his biggest regrets.

“And you know, if you look at the number of Americans killed since 9/11 by terrorism, it’s less than 100. If you look at the number that have been killed by gun violence, it’s in the tens of thousands. And for us not to be able to resolve that issue has been something that is distressing. But it is not something that I intend to stop working on in the remaining 18 months.”

Do you believe Obama’s biggest failure in office has been Libya?

[Photo by Joshua Lott/Getty Images]