Biden must emulate Truman's approach to counter Putin's ambitions in Ukraine and beyond.

When a well-meaning incrementalist clashes with a ruthless opportunist.

The opportunist seizes opportunity.

The traditional politician in the United States faces a historic confrontation with the world's wiliest authoritarian, who believes that the ends justify any means.

The authoritarian takes the initiative.

When President Joe Biden, 79, is confronted by President Vladimir Putin, 69, who is more determined than ever after 30 years of authoritarian rule, our messy democracy takes a beating.

If President Biden fails to transform the ongoing Ukrainian crisis into an opportunity by uniting allies and resolving internal divisions as President Harry Truman did during a similar turning point, the consequences for Europe and the world could be long-lasting.

Putin, with China's support, will continue his campaign to reverse the Cold War's outcome, where countries would navigate the future together based on new principles.

In Berlin this week, Secretary of State Anthony Blinken stated that the principles established after two world wars and a cold war do not allow one country to change another's borders by force, dictate its policies or choices, or exert a sphere of influence that would subjugate sovereign neighbors.

Blinken's words are powerful and should be repeated because they were drowned out by the noise of the news this week.

Allowing Russia to violate those principles without consequences would lead to a more dangerous and unstable time, as it did during the Cold War when this continent and city were divided, patrolled by soldiers, and threatened by all-out war. This would also signal to others worldwide that these principles are disposable, resulting in catastrophic outcomes.

It is argued that the US, with its own democracy in disarray and the president's popularity declining, may not be the best candidate to lead the defense of post-Cold War principles.

After Franklin Roosevelt's death in April 1945, Harry Truman became president, leading the Democratic party through a division between big-city progressives and southern conservatives during the end of World War II.

Although the American electorate was generally more conservative, he still supported far-left initiatives such as expanding the welfare state and increasing government intervention in the economy.

In 1946, Truman's Democratic party lost 54 seats in the House and 11 seats in the Senate, giving Republicans control of both chambers for the first time since 1932.

Despite the Republican party's internal disputes between its right and moderate wings, particularly regarding foreign policy, the conservative isolationist old guard, led by Ohio Senator Robert Taft, was competing for influence against the internationalist wing, with members like Massachusetts Senator Henry Cabot Lodge.

In Georgia, Governor Eugene Talmadge won a fourth term by campaigning to remove blacks from voting lists, with white supremacy being the main electoral theme.

The ongoing political polarization persisted even after Truman left office in January 1953, with his approval rating reaching a record low of 22% the previous year due to a prolonged Korean war, an economic downturn, labor strikes, and government corruption.

He is now regarded as one of America's greatest presidents due to his response to the Soviet challenge, which included the Marshall Plan of 1948, the Berlin Air Lift of 1948-49, and NATO's creation in 1949. His political, diplomatic, military, and economic initiatives laid the groundwork for an internationalist U.S. foreign policy that ultimately led to the end of the Cold War and the collapse of the Soviet Union in 1990.

As pundits advise President Biden to adjust his course to prevent an administration failure, he should take their suggestions into account.

An administration official identified three critical mistakes that needed to be resolved urgently: inadequate management of the ongoing Covid-19 crisis, lack of recognition of the political factors that undermined his "Build Back Better" bill, and, above all, failure to comprehend the inflationary risks that could jeopardize his re-election prospects.

President Biden's ability to address domestic challenges is crucial, but it may be the easy part. Truman's success in international affairs is what cemented his place in history and shaped the post-war era. Similarly, Biden has recognized our current time as an "inflection point" and has been right to see it as such.

During a news conference on Wednesday, Biden sparked controversy by implying that there would be disagreement among allies regarding how to handle a "minor incursion" into Ukraine.

The Washington Post editorial board was correct in stating that the president was telling the truth, despite U.S. officials correcting his statement to appease Ukrainian leaders and domestic critics.

Despite the ongoing Russian military buildup, Putin's actions are likely to be more complex and unpredictable, with the goal of causing discord among NATO allies and U.S. domestic politics over the best response.

In his meeting with Russian Foreign Minister Sergei Lavrov on Friday, Secretary of State Blinken may have bought some time for additional talks with the Russians. However, as the Atlantic Council's military analysts suggest, this could also provide more time to finalize military preparations for an invasion.

The issue isn't Putin's next move but rather the concerning pattern of his actions, which includes Russia's invasion of Georgia in 2008, annexation of Crimea in 2014, and now this test for President Biden.

In 1952, Truman emphasized the need for policies that, although rooted in self-interest, went beyond it and served as a link between the objectives of the United States and the aspirations of other free nations.

—Frederick Kempe is the President and Chief Executive Officer of the Atlantic Council.