Michael Vickers was undersecretary of defense for intelligence from 2011 to 2015 and assistant secretary of defense for special operations, low-intensity conflict and interdependent capabilities from 2007 to 2011. Michael Morell was deputy director of the CIA from 2010 to 2013, and twice served as acting director during that time. They have both endorsed Democrat Hillary Clinton for president.

Donald Trump showed again during Monday’s presidential debate the many ways in which he is unfit to be president. But nowhere did he reveal himself to be as temperamentally unfit, unserious, unprepared and incoherent as he did on the topic of national security.

Trump continued to question the global alliance system that has served U.S. national security interests so well since World War II. He continues to see our relationships with our closest allies and partners solely in terms of cost — who is paying how much of the bill. He does not see all the benefits that have accrued to the United States from this system, including the stability of Europe and East Asia that has made this a more secure and prosperous nation.

Trump spoke off the cuff about the most important responsibility of our commander in chief: U.S. nuclear weapons policy. Apparently unaware of the meaning of the words, he first said he believed in “no first use” of nuclear weapons, then contradicted himself by saying he would keep his options open as president. One of us (Michael Vickers) had oversight for U.S. nuclear weapons policy during the George W. Bush administration, and we can say unequivocally that absolute clarity is critical to the strength of our nuclear deterrent. And these comments come on top of Trump’s already-reckless pattern of remarks on allowing more countries to obtain nuclear weapons and the potential scenarios in which he would consider using such weapons.

Trump failed to articulate a plan to defeat the Islamic State, and he baldly lied about initially opposing the Iraq War. He continued his silly argument that to talk about his plan would give away secrets to the enemy. Nonsense. As two people who fought terrorists for almost two decades, we can assure Trump that offering the broad outlines of a policy gives nothing away. Michael McCaul (R-Tex.) , the talented chairman of the House Homeland Security Committee, just produced a thoughtful, nonpartisan policy paper on dealing with terrorism and protecting the homeland. Does Trump think that paper, produced by a fellow Republican, gives away secrets? We do not.

Trump has repeatedly claimed on the campaign trail, as he did again Monday night, that the United States would have prevented the emergence of the Islamic State if we had “taken the oil” in the aftermath of the Iraq War. Trump is apparently unaware that the terrorist group got its oil from fields in Syria, not Iraq. Trump likewise dubiously asserted that had the United States maintained 10,000 troops in Iraq after 2011 — against the wishes of the Iraqi government — it would have prevented the Islamic State from becoming a threat. Again, Trump is seemingly unaware of the facts. The Islamic State’s most rapid growth occurred when it crossed the border into Syria, where most of its forces remain today.

And Trump was not serious when he was discussing one of the most significant threats of our time: cyber. In discussing Russia’s possible involvement in the recent hack of the Democratic National Committee, he posited that a 400-pound person sitting on a bed could have been responsible. It is highly unlikely that a lone hacker conducted this attack. Trump did not want to admit that the most likely culprit was Russian President Vladimir Putin, whom Trump actually encouraged to conduct cyber espionage against his opponent, Hillary Clinton.

As bad as he was on the issues, Trump was even worse on temperament and style. He was clearly not prepared for the debate, rambling through answers with many digressions that had nothing to do with what he was asked or even the point he was trying to make. A commander in chief needs many qualities, and one of them is being prepared. If Donald Trump thinks preparation is overrated and that a seat-of-the-pants approach makes sense for the most important debate of his life, why do we think he would treat meetings in the White House Situation Room any differently?