Joe Biden is widely expected to nominate Michele Flournoy to the position of Defense Secretary. In 2016, Flournoy was touted as the Pentagon head of choice for a possible Hillary Clinton administration.

Flournoy first joined the Pentagon under Bill Clinton’s presidency and served as Under Secretary of Defense for Policy during the first term of the Obama administration. She co-founded the Center for a New American Security, a DC-based think tank, in 2007. Flournoy was also tapped up for a role in the Pentagon by Trump’s first Defence Secretary Jim Mattis.

During the Obama years, Flournoy supported doubling the US presence in Afghanistan and was involved in convincing the then President to intervene in the Libyan civil war.

Illinois Senator Tammy Duckworth, a former Lieutenant Colonel in the US Army who currently sits on the Senate Committee on Armed Services, is also said to be a potential candidate for SecDef. Duckworth was awarded a Purple Heart for her service. In 2004, she lost both her legs when a rocket-propelled grenade hit the Blackhawk helicopter she was co-piloting over Iraq.

Writing in response to the Military Officers Association of America (MOAA) ahead of the election, Biden said: “President Trump has abandoned all fiscal discipline when it comes to defence spending. His budget is dominated by investments in ageing legacy capabilities. At a time when we’re winding down our main combat efforts from the last two decades, we need to make smarter investments in our military.”

Biden is unlikely to enact large-scale cuts to defence spending but has instead argued that the US needs to ‘make smart investments’ in technologies and innovations in cyber, space, uncrewed systems and artificial intelligence to allow the US to better meet future threats.

Writing to the MOAA, Biden added: “We have to move away from investments in legacy systems that won’t be relevant for tomorrow’s wars, and we have to rethink the contributions we and our allies make to our collective security.”

Biden has said that the US also needs to ‘invest in our other elements’ of the country’s national power, saying the US had become ‘over-dependent’ on the armed forces to advance its security agenda. This will likely see a Biden administration strengthen US investment in soft power through diplomacy, economics and science and technology.

NATO Secretary-General Jens Stoltenberg said in a statement that he ‘warmly’ welcomed the election of Joe Biden, adding that he knew the President-elect to be a ‘strong supporter of NATO and the transatlantic relationship.’

Stoltenberg added: “US leadership is as important as ever in an unpredictable world, and I look forward to working very closely with President-elect Biden, Vice President-elect Kamala Harris and the new administration to further strengthen the bond between North America and Europe.”

Both NATO envoys and Biden have in the past said they would seek an early summit next year. Biden has strongly supported the expansion of NATO, supporting the entry of North Macedonia to the alliance.

In 2019, Biden wrote that as president he would call for a review of NATO member states’ ‘democratic commitments’ and work with allied member states to ‘draft a new strategic concept for NATO’ acknowledging the challenges of Russian aggression, democratic backsliding and technology like artificial intelligence.

Biden added: “At NATO summits and in bilateral engagements, a Biden presidency will prioritise strengthening national democratic institutions in member states that are not living up to NATO’s core values. Democratic and free institutions are the bedrock of our alliance, and they must be defended to strengthen our collective security.”

Royal United Services Institute (RUSI) research fellow and editor of RUSI Defence Systems Justin Bronk told us: “The Biden Presidency is likely to be heavily focused on domestic issues, but in terms of NATO we will almost certainly see an effort to renew damaged relations with alliance members (especially Germany), a continued focus on the threat from Russia, and continued pressure on European capitals to spend more on defence – albeit much more tactfully delivered than under President Trump.”

As President, Biden is to seek an extension to the New START Treaty that governs the nuclear arsenals of Russia and China. The treaty was signed by the Obama administration in 2010, while Biden was serving as vice president.

Under the Trump administration, the US pulled out of the Intermediate-Range Nuclear Forces (INF) Treaty, leaving New START as the only international treaty governing nuclear weapons.

Biden has also signalled that if Iran returned to compliance with the Iran nuclear deal, his administration would re-enter the agreement.

Discussing American leadership, Biden’s campaign website reads: “President Biden would take other steps to demonstrate our commitment to reducing the role of nuclear weapons. As he said in 2017, Biden believes the sole purpose of the US nuclear arsenal should be deterring — and if necessary, retaliating against — a nuclear attack. As president, he will work to put that belief into practice, in consultation with our allies and military.”

Commenting on the US' involvement in drawn-out conflicts in the Middle East, Biden wrote to the MOAA saying: “I will end the forever wars in Afghanistan and the Middle East, which have cost us untold blood and treasure. I will bring US combat troops home from Afghanistan in my first term. Any residual US military presence would be focused only on counterterrorism operations and supporting local partners.

“For the time being, we will also likely need to maintain a residual presence in Iraq and Syria — with our coalition partners — to prevent a re-emergence of ISIS. But we do not need large deployments of combat forces to maintain our security.”

However, Biden added that on taking office he would "hear from both our military leadership and our civilian security experts as well as our allies" before making any final decisions on changes to the US's overseas military presence.