In the beginning, it was just a T-shirt: basic, olive green; the kind worn under military fatigues or hauled out from the bottom of a wardrobe for workouts and weekends. Sometimes it was more brown than green. Sometimes there was a cross over the heart, with a coat of arms in the center.

But over the last four weeks, as the Ukrainian president, Volodymyr Zelensky, has shed his former navy suits, white shirts and ties — the uniform of the politician — for the T-shirt, wearing it in his daily videos to his country; in his speeches to the European Parliament, to the British Parliament, to the American Congress; in his interview over the weekend with CNN (and his widely tweeted Zoom call with supporters Ashton Kutcher and Mila Kunis). It has become something more: a symbol of the strength and patriotism of the Ukrainian people, a host of values and purpose packed into an outline everyone knows.

Along with the photos of bodies lying lifeless on the streets, and bombed out theaters and apartment buildings, it will be one of the defining images of the conflict. It is a metaphor in cloth for the growing narrative of a Russian Goliath and Ukrainian David, of hubris and heroism, that is being played out in blood and arms.

The T-shirt is a reminder of Mr. Zelensky’s origins as a regular guy; a connection between him and the citizen-soldiers fighting on the streets; a sign he shares their hardship. He could, as the commander in chief, have remained in his formal wear, as Churchill did when he visited the bombed-out sites of Coventry in his black homburg, overcoat and bow tie in World War II. That Mr. Zelensky choose instead to adopt what may be the single most accessible garment around — the T-shirt — is as clear a statement of solidarity with his people as any of his rhetoric.

Indeed, when he spoke to Congress and the economist Peter Schiff tweeted afterward, “I understand times are hard, but doesn’t the President of the #Ukraine own a suit?” suggesting that by wearing a T-shirt Mr. Zelensky had disrespected the American lawmakers, it was Mr. Schiff who missed the point.

The T-shirt was not a sign of disrespect to those Mr. Zelensky was addressing; it was a sign of respect and allegiance to those who he was representing; a reminder of what was going on just outside his doors (the cross, by the way, was the insignia of the Ukrainian military). By wearing their uniform, rather than the uniform of the people in the room, he was making the surreal real, just as the video he later showed of bombs raining down on his cities did.

To say that Mr. Zelensky, a former actor, clearly understands how clothing speaks to character and can be used as a form of propaganda is not to demean his position or role in the history of the moment.

After all, dress, like music and films and literature, has long been used to deliver political messages and sway opinion. It happened in the 1950s (and thereafter) with the C.I.A. secretly distributing “Doctor Zhivago” to destabilize the Soviet Union; and during the Cold War with the covert use of rock ’n’ roll to chip away at the Berlin Wall. It was exemplified by Fidel Castro’s preference for the army green military shirt and cap as his uniform, and the Mao suit as adopted by Mao Zedong and the Chinese Communist Party, both choices meant to conflate the leaders and their populace. Also, George W. Bush landing on the USS Abraham Lincoln aircraft carrier in full military drab flight suit to declare victory in the Iraq war.

And whether or not Congress recognizes the T-shirt, almost anyone watching can. Dress is one of the ways we connect to people in circumstances beyond our imagining because it renders them familiar. Consider how many images of extremists have become known by the clothes in the pictures: the “woman in the white thoub,” standing on a car during the Sudanese protests in 2019; the “man in the white shirt,” standing in front of the tanks as they rolled into Tiananmen Square in 1989; the “woman in a red dress,” being sprayed by Turkish soldiers during an anti-government demonstration in Istanbul in 2013. More than examples of individual heroism (though they are that), they become examples of the heroism that is possible in all individuals.

By their dress, we relate to them. The power of the pictures lies in the way they capture an apparently regular person — someone wearing an item of clothing that exists in the closet of almost everyone watching, no matter their country or their circumstance — in an irregular situation. It allows everyone seeing, to see themselves.

With his nondescript T-shirt, in his generic white-walled office, next to the Ukrainian flag, Mr. Zelensky has combined these two traditions into one. He is both the man in the olive green tee and the father of the nation.

And in his dress, as in his actions and his words, Mr. Zelensky has placed himself in opposition to the guy on the other side: President Vladimir V. Putin of Russia, famous for his elaborate, gilded palaces and his love of a luxury label; his Cartier sunglasses and Patek Philippe watches.

Even addressing the crowd during a rally in Moscow on March 18 celebrating Russia’s annexation of Crimea and “universal values,” Mr. Putin wore a Loro Piana puffer that costs more than $10,000 (a change.org petition was started not long after to demand that the Italian brand, owned by LVMH, denounce their apparent customer) and a Kiton cashmere roll-neck sweater, brand badges of wealth and remove. It’s an example that has inspired similar choices among his acolytes, with the Chechen strongman Ramzan Kadyrov spotted in what GQ said were Prada combat boots.

It is a power dialectic writ in cloth; the elitist versus the Everyman; thesis and antithesis. Marx, of all people, would understand.