Elbridge Andrew Colby (born December 30, 1979) is an American national security policy professional who is the under secretary of defense for policy since April 9, 2025. He previously served as deputy assistant secretary of defense for strategy and force development from 2017 to 2018 during the first Trump administration. He played a key role in the development of the 2018 U.S. National Defense Strategy, which, among other things, shifted the U.S. Defense Department's focus to China. He is the grandson of former CIA director William Colby.
In June 2018, Colby was appointed as director of the Defense Program at the Center for a New American Security (CNAS). In 2019, he co-founded the Marathon Initiative, a grand strategy think tank, with Wess Mitchell. In December 2024, President-elect Donald Trump nominated Colby to serve as the under secretary of defense for policy in the second Trump administration.
Identifying as a realist, Colby believes China is the principal threat faced by the United States. He believes the US should shift its military resources to Asia to prevent a Chinese takeover of Taiwan. Colby supports reducing military aid to Ukraine. During the AUKUS review in 2025, Colby pressured Australia to confirm what role it would play in a war with China over Taiwan.
Education and early career Colby moved to Tokyo in 1986 at the age of eight when his father was appointed head of First Boston's Tokyo office, and he returned when he was thirteen. While in Tokyo, he attended the American School in Japan in Chōfu. Following his return to the U.S., Colby attended and graduated from Groton School (Class of 1998), where he served as editor of the school newspaper. Colby graduated from Harvard College in 2002, and from Yale Law School in 2009. His early career included over five years of service with the Department of Defense, the Department of State, and in the intelligence community, including a period of service with the Coalition Provisional Authority in Iraq in 2003. Colby also served in the Office of the Director of National Intelligence in 2005–2006.
From 2010 to 2013, Colby worked as an analyst at CNA, a federally funded nonprofit research and analysis organization. From 2014 to 2017, Colby was the Robert M. Gates fellow at the Center for a New American Security. In 2015, Colby was considered for a major position in Jeb Bush's 2016 presidential campaign, but was not hired after "prominent, interventionist neoconservatives" objected.
First Trump administration In May 2017, Colby was appointed Deputy Assistant Secretary of Defense for strategy and force development, a role in which he served into 2018. In this role, Colby was responsible for defense strategy, force development, and strategic analysis for policy for the secretary of defense. Colby served as the primary Defense Department representative in the development of the 2017 National Security Strategy.
While deputy assistant secretary, Colby served as the lead official in the development and rollout of the department's strategic planning guidance, the 2018 National Defense Strategy (NDS). The NDS posited: "Inter-state strategic competition, not terrorism, is now the primary concern in U.S. national security", and "the central challenge to U.S. prosperity and security is the reemergence of long-term strategic competition", primarily from China and Russia. Going further, Colby said the "central challenge facing the department of defense and the joint force [is] the erosion of U.S. military advantage vis a vis China and Russia." In April 2023, Politico reported that in re-orienting American defense resources away from the Middle East and towards China, Colby faced considerable bureaucratic infighting from U.S. Central Command and the Joint Staff, but received support from the Air Force and the Navy.
Interlude After leaving the Department of Defense in 2018, Colby returned to the Center for a New American Security (CNAS), where he continued to work on defense issues until 2019. Colby also worked for WestExec Advisors, a consultancy founded by Michele Flournoy and Antony Blinken. He then launched The Marathon Initiative, a think tank devoted to developing strategies for the US to compete with global rivals. In 2021, Colby expanded on his views in his first book, The Strategy of Denial: American Defense in an Age of Great Power Conflict, which The Wall Street Journal named a Ten Best Book of 2021.
Second Trump administration
Nomination and confirmation
On December 22, 2024, President-elect Trump nominated Colby to serve as the under secretary of defense for policy for his second term as president. Despite the support of influential MAGA figures like Vice President JD Vance and influencer Charlie Kirk, his nomination drew criticism from Republican Party defense hawks like Senator Tom Cotton regarding his past comments that Iran's acquisition of a nuclear weapon would not be an existential risk for the United States. During his hearing before the United States Senate Committee on Armed Services on March 4, 2025, Colby said he would not hesitate to advise Trump on military options to stop Iran's nuclear program if necessary. He also confirmed his intention to increase U.S. military resources in the Indo-Pacific and called on Taiwan to increase its defense budget from 2.5% of GDP to 10%. Colby's nomination was confirmed by a 54–45 Senate vote on April 8, 2025.https://thehill.com/homenews/senate/5237883-senate-confirms-elbridge-colby-pentagon/ Senator Mitch McConnell was the only Republican to oppose Colby's nomination, leading to criticism from Republicans including JD Vance and Nate Morris.
Tenure In May 2025, Colby told British officials that the United States wanted the British Armed Forces to focus less on the Indo-Pacific and more in the Euro-Atlantic region. He also expressed concern about the UK sending the HMS Prince of Wales to the Indo-Pacific. In June 2025, Colby pushed for the Department of Defense to launch a review whether to scrap the AUKUS agreement with Australia and the United Kingdom. Colby also pushed for Japan to increase its military spending to 3.5% of its GDP, which led Japan to cancel a meeting between U.S. secretary of state Marco Rubio and U.S. defense secretary Pete Hegseth and Japanese Defense Minister Gen Nakatani and Foreign Minister Takeshi Iwaya in Washington, D.C.
In early July, the US paused deliveries of various munitions to Ukraine, an initiative that reportedly originated from Colby; both Congress and the State Department were not aware of the decision. Additionally, members of the Trump administration were not consulted on the halting of the arms shipments, with Trump himself claiming to be unaware of the decision. Trump later reinstated the arms shipments within days. Afterwards, a bi-partisan group of members of Congress demanded an explanation from Colby. After the European-White House crisis meeting was held in August 2025, Trump announced the US could provide security guarantees to Ukraine as part of a peace agreement to end the Russo-Ukrainian war. Colby reportedly told representatives of European allies that the US would play a minimal role in any security guarantees. Later that month, Ukraine was denied long-range missile strikes on Russia under a "review mechanism" that had been developed by Colby.
During a Senate Armed Services Committee hearing held in November 2025, several Republican senators criticized Colby's office for failure to communicate policy with members of Congress. During the hearing to confirm Austin Dahmer as Assistant Secretary of Defense for Strategy, Plans, and Capabilities, Senator Dan Sullivan of Alaska stated "I can't even get a response, and we're on your team" claiming that it was more difficult to get a response from Colby than it was to speak with Defense Secretary Pete Hegseth or even President Trump. Sullivan added that Colby "has been really bad on this. The worst in the administration." Senator Roger Wicker of Mississippi agreed, stating that Colby's policy office had been unusually difficult about information sharing relative to other organs of the Defense Department, while Senator Tom Cotton of Arkansas characterized Colby's office as a "pigpen-like mess" regarding communication. On 5 November, the Pentagon denied Colby had been purposely withholding information from Congress. Kingsley Wilson, the Pentagon's spokesperson, stated that Colby's team had "briefed Congress dozens of times, in both classified and unclassified settings, in addition to other meetings." Reuters described the incident as a "rare bipartisan show of frustration with the administration."
In December 2025, the Financial Times reported that many within the administration of Japanese Prime Minister Sanae Takaichi felt "deep disappointment" over the lack of public support she received from Trump over remarks about defending Taiwan after she stated that a Chinese invasion of Taiwan would constitute a "survival threatening situation" to Japan and prompt a response from the Japan Self-Defense Forces. This came after Colby had been reportedly pushing Japan to take such a stance.
2026 meeting with Vatican ambassador
In April 2026, The Free Press reported that on January 22, 2026, Colby summoned Vatican ambassador Cardinal Christophe Pierre to an "unprecedented" closed door "lecture" at the Pentagon. According to The Free Press, Colby, along with several colleagues, used the meeting to criticize Pope Leo XIV's annual "state of the world" speech given in January 2026, and told Pierre that the United States "has the military power to do whatever it wants—and that the Church had better take its side." Another official invoked the Avignon Papacy, a period during the 1300s where the French Monarchy used its military power to control the papacy.
Political views Colby identifies as a realist. He believes that China is the principal threat faced by the United States, and that Asia should be the priority of U.S. efforts and resources. He advocates for the U.S. to shift its military planning and resources to prepare for a conflict over Taiwan, and supports bolstering U.S. industrial capacity. In a Time article he co-authored with Heritage Foundation president Kevin Roberts, Colby wrote: "[W]e need to be absolutely clear: Without question, the top external threat to America is China—by far." He is a "prioritizer", believing the U.S. to have limited military resources, and thus supporting a reorientation of U.S. military resources away from the Middle East and Europe to Asia and China. Foreign Policy describes him as "the loudest and perhaps most cogent voice in Washington advocating a complete shift away from Europe, NATO, and Russia and toward the growing challenge from China".
East Asia