Policy & Advocacy

Backgrounder on Nuclear Weapons

Year Published
  • 2018
  • English

Printable Version

An ethics and a law based on the threat of mutual destruction – and possibly the destruction of all mankind – are contradictory to the very spirit of the United Nations. We must therefore commit ourselves to a world without nuclear weapons, by fully implementing the Non-Proliferation Treaty, both in letter and spirit.

—Pope Francis to UN Conference to Prohibit Nuclear Weapons, March 2017


In 1963 Saint John XXIII wrote in Pacem in Terris: "Nuclear weapons must be banned. A general agreement must be reached on a suitable disarmament program, with an effective system of mutual control." Support for nuclear disarmament and non-proliferation has been emphasized by Blessed Paul VI, Saint John Paul II, Benedict XVI and Francis.  The U.S. Bishops have worked for nuclear disarmament and non-proliferation for decades.  

Nuclear Non-Proliferation Treaty:  The Nuclear Non-Proliferation Treaty (NPT) is the cornerstone of global efforts to curb and reverse the spread of nuclear weapons.  One-hundred-and-ninety-eight countries have ratified the treaty, including the five acknowledged nuclear powers: United States, Russia, United Kingdom, France, and China.  Only four nations have not: India, Israel, Pakistan and North Korea.  The NPT prohibits non-nuclear states from acquiring nuclear weapons (non-proliferation), requires nuclear states to reduce and eliminate nuclear weapons (disarmament), and guarantees access to peaceful nuclear technology (nuclear power).

Years ago, President Ronald Reagan and General Secretary Mikhail Gorbachev called for abolishing all nuclear weapons. Former Secretaries of State and Defense George Shultz, William Perry and Henry Kissinger and Senator Sam Nunn have promoted a nuclear-free world.  Past presidents Barack Obama and Russian Dmitry Medvedev committed "our two countries to achieving a nuclear free world." The Trump administration's plans for the U.S. nuclear stockpile will be articulated in a forthcoming Nuclear Posture Review. The administration will also have the opportunity to pursue an extension of New START beyond its 2021 expiration date, an extension supported by many experts and Russia as "fundamental to global security."

New START Treaty:  In 1991, the United States and Soviet Union ratified the Strategic Arms Reduction Treaty (START).  This treaty limited the number of nuclear warheads and delivery vehicles (missiles and bombers) that each country could deploy.  The treaty also incorporated a solid set of verification measures the two nations could use to monitor each other's nuclear arsenals and compliance with the treaty.

Today the United States and Russia still hold about 90% of all nuclear weapons, large arsenals left over from the Cold War.  START expired in 2009 and with it the verification protocols, but both nations agreed to keep its provisions in effect while they negotiated a START follow-on treaty.  Implementation of a New START Treaty was critical because verification ensures transparency and even modest reductions in the number of weapons can set the stage for future reductions. The U.S. and Russia signed a new Strategic Arms Reduction Treaty (New START) on April 8, 2010, which was ratified by the Senate on a solid bipartisan vote of 71 to 26. The Holy See has "welcome[d] and recognize[d] the ongoing successful implementation of New START." The New START Treaty: reduces deployed strategic warheads to 1550, 30 percent below the existing ceiling; limits both nations to no more than 700 delivery vehicles; and includes new verification requirements.

Comprehensive Test Ban Treaty:  Despite U.S. involvement in initiating the negotiations, in 1999 the U.S. Senate failed to ratify the Comprehensive Test Ban Treaty (CTBT) that would stop nuclear testing. Some Senators who voted "no" expressed concerns about the ability of the United States to maintain its arsenal in the absence of testing and others were concerned about verifying compliance with the treaty. Prominent scientists have argued that the U.S. can safely maintain its nuclear arsenal without testing and that the ability of the international community to verify compliance is amply demonstrated by detections of tests in North Korea. One hundred and fifty-one other nations have ratified the CTBT, including UK, France, and Russia. The United States' failure to ratify the CTBT prevents the treaty's immediate entry into force. The Holy See declared, "There is no reason for procrastination." It is not known when the CTBT may be submitted to the Senate for ratification.

P5+1 Agreement with Iran:  In recent years, serious questions were raised regarding Iran's nuclear program. In response, talk of military intervention increased, and crippling international sanctions were instituted to the detriment of Iran's economy and its citizens. Following the election of Iranian President Rouhani, the United States, United Kingdom, Russia, China, Germany and France (P5+1) entered into diplomatic negotiations with Iran regarding its nuclear program and international sanctions.

In July 2015, after 20 months of concerted collaboration, the P5+1 reached an agreement with Iran that aims to curb Iran's development of nuclear weapons while allowing for the use of nuclear energy for peaceful purposes. In September, a cloture vote in the Senate that would have allowed rejection of the P5+1 deal failed, so the agreement stands. Recent Iranian launches of ballistic missiles, inconsistent with UN Security Council Resolution 2231, but not in violation of the P5+1 Agreement, have raised concerns. In October 2017, President Trump announced he would not certify to Congress that Iran was in compliance, despite U.S. and international evidence that Iran is observing the agreement.  To date, Congress has not acted to undermine the agreement.

Nuclear Ban Treaty:  In a major and encouraging development, a majority of the world's nations supported adoption of the Treaty on the Prohibition of Nuclear Weapons with the goal of leading towards their total elimination in July 2017.  The vote was 122 in favor (including the Holy See), 1 against, and 1 abstention.  Unfortunately, 69 nations did not vote, including all nuclear weapon states and all but one NATO member.

USCCB POSITION: The United States and other nuclear powers must move away from reliance on nuclear weapons for security. USCCB urges the Administration and Congress to view arms control treaties not as ends in themselves but as steps along the way to achieving a mutual, verifiable global ban on nuclear weapons. A global ban is more than a moral ideal; it should be a policy goal.

USCCB advocated for ratification of the P5+1 Agreement with Iran in 2015. The USCCB Committee on International Justice and Peace, reflecting the longstanding position of the Holy See, urged our nation to pursue diplomacy to ensure Iran's compliance with its obligations under the Nuclear Non-Proliferation Treaty. The Church did not weigh-in on the technical details of the agreement, but consulted with many experts on the broad outlines required for a credible and verifiable agreement.

Led by Pope Francis, the U.S. bishops and Holy See continue to support the P5+1 Agreement with Iran as a "definitive step toward greater stability and security in the region." The Holy See notes that the agreement "requires further efforts and commitment by all the parties involved in order for it to bear fruit."

During the negotiations on the Nuclear Ban Treaty, USCCB and the Conference of European Justice and Peace Commissions issued a joint call for a strategy to eliminate nuclear weapons globally

USCCB plans to support Senate ratification of the CTBT if and when it is introduced. The Church opposes the use of nuclear weapons, especially against non-nuclear threats. The U.S. should commit to never use nuclear weapons first and to reject use of nuclear weapons to deter non-nuclear threats. The Church urges that nuclear deterrence be replaced with concrete measures of disarmament based on dialogue and multilateral negotiations.


  1. Urge bold and concrete commitments to accelerate verifiable nuclear disarmament, including taking weapons off "launch on warning" status to prevent a catastrophic accident and making deeper cuts in nuclear arsenals.
  2. Oppose the investment of hundreds of billions of dollars in modernizing nuclear weapons systems that ultimately we must work to dismantle.
  3. Support serious negotiations on a fissile material cut-off treaty and other prudent measures.
  4. If it is introduced, urge Senators to support ratification of the Comprehensive Test Ban Treaty (CTBT) to bring it into force.
  5. Encourage Congress and the Administration not to take any actions that could undermine the agreement between the P5+1 and Iran.
For further information: visit https://www.usccb.org/issues-and-action/human-life-and-dignity/war-and-peace/nuclear-weapons/index.cfm or contact Stephen Colecchi, Director, Office of International Justice and Peace, USCCB, 202-541-3196 (phone), 202-541-3339 (fax), @email.
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