Prince Charles and Camilla were among an array of foreign dignitaries on Thursday to attend Greek Independence Day celebrations, albeit scaled back because of the coronavirus pandemic.
The commemoration marked 200 years since the start of Greece's independence war with the Ottoman Empire.
"Today the nation celebrates," Prime Minister Kyriakos Mitsotakis said, as the Greek flag was solemnly raised over the Acropolis in Athens.
"Two centuries ago, a handful of determined fighters in and outside Greece raised the banner of independence ... with the help of their allies, they fought heroically and won their freedom."
His words were prologue to a raft of events planned all over Greece and among diaspora communities overseas.
During a sunny interlude that later turned to snow, a procession of tanks, artillery, mounted troops and children dressed in traditional costumes made its way through the capital. Jets and helicopters flew overhead.
French Rafales and American F-16s were part of the show, while a cannon on Lycabettus Hill overlooking Athens earlier fired a salute of 21 shots.
Security was tight, with 4,000 police, drones and snipers deployed in Athens, a police source said.
Because of Covid restrictions, no spectators were allowed to attend the parade, aside from a small number of reporters.
Prince Charles and Camilla were joined by Russian Prime Minister Mikhail Mishustin, Cypriot President Nicos Anastasiades and French Defence Minister Florence Parly, as they placed wreaths at the Tomb of the Unknown Soldier, Greece's foremost military monument.
US President Joe Biden and French counterpart Emmanuel Macron – who pulled out of the event at the last minute owing to the latest Covid-19 lockdown in France – and EU leaders sent messages of support.
Britain, France and Russia were instrumental in helping Greece attain its independence in 1830 after nearly a decade of warfare against overwhelming odds.
Americans, including a nephew of George Washington, were among volunteer combatants.
At the time, the Ottoman Empire extended through the Balkans and modern-day Turkey to North Africa, the Arabian Peninsula and the Caucasus.
"As the wellspring of western civilisation, Greece's spirit runs through our societies and our democracies," Prince Charles said at a dinner at the presidential mansion on Wednesday.
"Without her, our laws, our art, our way of life would never have flourished as they have."
Sympathy for the cause of Greece in 1821 sparked a movement in Europe and the US known as Philhellenism, with proponents including former US president Thomas Jefferson, French novelist Victor Hugo, German poet Johann Wolfgang von Goethe, Russian author Alexander Pushkin and English poets Percy Bysshe Shelley and Lord Byron.
Hundreds of Philhellene volunteers fought and died for Greece's liberation, with Byron among them.
A joint effort by France, Russia and Britain eventually defeated a Turkish-Egyptian fleet in the pivotal 1827 Battle of Navarino, and further military reversals forced the Ottoman Empire to recognise Greece's sovereignty in 1830.
Macron invokes Turkish tensions
"Your liberty is our [liberty)]" Mr Macron said in Greek in a recorded message.
"We are here, and we will stand by your side when history is unfair towards you, when solidarity may be lacking, when menace returns," he said, in an apparent reference to ongoing tensions with Turkey.
Ankara last year sent a research ship accompanied by a navy flotilla into waters near the Turkish coast that Greece claims on the basis of post-war treaties.
In contrast to other EU and Nato allies, France strongly backed Greece during the showdown.
EU leaders later on Thursday will begin a two-day video summit that will address relations with Ankara.
Mr Mitsotakis on Thursday said victory was also in sight against the pandemic, which has claimed more than 7,600 lives in Greece.
"Our country comes out of this adventure stronger," he said.
