At least 50 former Republican policy experts and security officials wrote a public letter opposing the presidential bid of Donald Trump.

The undersigned individuals have all served in senior national security and/or foreign policy positions in Republican Administrations, from Richard Nixon to George W. Bush. We have worked directly on national security issues with these Republican Presidents and/or their principal advisers during wartime and other periods of crisis, through successes and failures. We know the personal qualities required of a President of the United States.

None of us will vote for Donald Trump.

From a foreign policy perspective, Donald Trump is not qualified to be President and Commander-in-Chief. Indeed, we are convinced that he would be a dangerous President and would put at risk our country’s national security and well-being.

Most fundamentally, Mr. Trump lacks the character, values, and experience to be President. He weakens U.S. moral authority as the leader of the free world.

He appears to lack basic knowledge about and belief in the U.S. Constitution, U.S. laws, and U.S. institutions, including religious tolerance, freedom of the press, and an independent judiciary. In addition, Mr. Trump has demonstrated repeatedly that he has little understanding of America’s vital national interests, its complex diplomatic challenges, its indispensable alliances, and the democratic values on which U.S. foreign policy must be based.

At the same time, he persistently compliments our adversaries and threatens our allies and friends. Unlike previous Presidents who had limited experience in foreign affairs, Mr. Trump has shown no interest in educating himself. He continues to display an alarming ignorance of basic facts of contemporary international politics.

Despite his lack of knowledge, Mr. Trump claims that he understands foreign affairs and “knows more about ISIS than the generals do.”

Mr. Trump lacks the temperament to be President.

In our experience, a President must be willing to listen to his advisers and department heads; must encourage consideration of conflicting views; and must acknowledge errors and learn from them.

A President must be disciplined, control emotions, and act only after reflection and careful deliberation. A President must maintain cordial relationships with leaders of countries of different backgrounds and must have their respect and trust. In our judgment, Mr. Trump has none of these critical qualities. He is unable or unwilling to separate truth from falsehood. He does not encourage conflicting views.

He lacks self-control and acts impetuously. He cannot tolerate personal criticism. He has alarmed our closest allies with his erratic behavior.

All of these are dangerous qualities in an individual who aspires to be President and Commander-in-Chief, with command of the U.S. nuclear arsenal. We understand that many Americans are profoundly frustrated with the federal government and its inability to solve pressing domestic and international problems. We also know that many have doubts about Hillary Clinton, as do many of us.

But Donald Trump is not the answer to America’s daunting challenges and to this crucial election. We are convinced that in the Oval Office, he would be the most reckless President in American history.

  • Donald B. Ayer

Former Deputy Attorney General

  •  John B. Bellinger III

Former Legal Adviser to the Department of State; former Legal Adviser to the National Security Council, The White House

  • Robert Blackwill

Former Deputy National Security Advisor for Strategic Planning, The White House

  • Michael Chertoff

Former Secretary of Homeland Security; former Assistant Attorney General for the Criminal Division, Department of Justice

  • Eliot A. Cohen

Former Counselor of the Department of State

  • Eric Edelman

Former Under Secretary of Defense for Policy; former National Security Advisor to the Vice President, The White House

  • Gary Edson

Former Deputy National Security Advisor, The White House

  • Richard Falkenrath

Former Deputy Homeland Security Advisor, The White House

  • Peter Feaver

Former Senior Director for Strategic Planning, National Security Council, The White House

  • Richard Fontaine

Former Associate Director for Near East Affairs, National Security Council, The White House

  • Jendayi Frazer

Former Special Assistant to the President and Senior Director for African Affairs; former Assistant Secretary of State for African Affairs

  • Aaron Friedberg

Former Deputy National Security Advisor to the Vice President, The White House

  • David Gordon

Former Director of Policy Planning, Department of State Michael Green Former Special Assistant to the President and Senior Director for Asia, National Security Council, The White House

  • Brian Gunderson

Former Chief of Staff, Department of State

  • Paul Haenle

Former Director for China and Taiwan, National Security Council, The White House

  • Michael Hayden

Former Director, Central Intelligence Agency; former Director, National Security Agency

  • Carla A. Hills

Former U.S. Trade Representative

  • John Hillen

Former Assistant Secretary of State for Political-Military Affairs

  • William Inboden

Former Senior Director for Strategic Planning, National Security Council, The White House

  • Reuben Jeffery III

Former Under Secretary of State for Economic Energy and Agricultural Affairs; former Special Assistant to the President for International Economic Affairs, National Security Council, The White House

  • James Jeffrey

Former Deputy National Security Advisor, The White House

  • Ted Kassinger

Former Deputy Secretary of Commerce

  • David Kramer

Former Assistant Secretary of State for Democracy, Human Rights, and Labor

  • James Langdon

Former Chairman, President’s Foreign Intelligence Advisory Board, The White House

  • Peter Lichtenbaum

Former Assistant Secretary of Commerce for Export Administration

  • Mary Beth Long

Former Assistant Secretary of Defense for International Security Affairs

  • Clay Lowery

Former Assistant Secretary of the Treasury for International Affairs; former Director for International Finance, National Security Council, The White House

  • Robert McCallum

Former Associate Attorney General; former Ambassador to Australia

  • Richard Miles

Former Director for North America, National Security Council, The White House

  • Andrew Natsios

Former Administrator, U.S. Agency for International Development

  • John Negroponte

Former Director of National Intelligence; former Deputy Secretary of State; former Deputy National Security Advisor

  • Meghan O’Sullivan

Former Deputy National Security Advisor for Iraq and Afghanistan

  • Dan Price

Former Deputy National Security Advisor

  • Tom Ridge

Former Secretary of Homeland Security; former Assistant to the President for Homeland Security, The White House; former Governor of Pennsylvania

  • Nicholas Rostow

Former Legal Adviser to the National Security Council, The White House

  • Kori Schake

Former Director for Defense Strategy, National Security Council, The White House

  • Kristen Silverberg

Former Assistant Secretary of State for International Organizations

  • Stephen Slick

Former Special Assistant to the President and Senior Director for Intelligence Programs, National Security Council, The White House

  • Shirin R. Tahir-Kheli

Former Special Assistant to the President and Senior Director for Democracy, Human Rights and International Operations, National Security Council, The White House; former Ambassador and Senior Advisor for Women’s Empowerment, Department of State

  • William H. Taft IV

Former Deputy Secretary of Defense; former Ambassador to NATO

  • Larry D. Thompson

Former Deputy Attorney General

  • William Tobey

Former Deputy Administrator, National Nuclear Security Administration, Department of Energy; former Director for Counter Proliferation Strategy, National Security Council, The White House

  • John Veroneau

Former Deputy U.S. Trade Representative

  • Kenneth Wainstein

Former Assistant to the President for Homeland Security and Counterterrorism, The White House; former Assistant Attorney General for National Security, Department of Justice

  • Matthew Waxman

Former Deputy Assistant Secretary of Defense; former Director for Contingency Planning and International Justice, National Security Council, The White House

  • Dov Zakheim

Former Under Secretary of Defense

  • Roger Zakheim

Former Deputy Assistant Secretary of Defense

  • Philip Zelikow

Former Counselor of the Department of State Robert

  • Zoellick Former

U.S. Trade Representative; former Deputy Secretary of State