Wednesday was supposed to be the day Turks celebrated the heritage of Kemal Atatürk, the resistance hero who 80 years ago dragged his people from the wreckage of the Ottoman Empire into secular republican modernity.
Instead, it degenerated into a squabble, nominally over women's clothing, that had more to do with what it is to be modern in this mainly Muslim country straddling two continents and two civilizations.
As always with the most serious quarrels, this one began with a trifle - the president's annual party.
While foreign diplomats and opposition lawmakers - pillars of Turkey's Westernized and staunchly pro-secular elite - were invited to bring their spouses, male members of the conservative Justice and Development Party (AKP) were asked to leave their wives at home.
The reason? Most wear head scarves, legally forbidden in universities and public offices around the country. AKP deputies were far from alone in deploring the president's decision. But he had his supporters, too. "[Government supporters] claim this decision is against human rights and democracy," fumes Gulay Ertekin, who sells insurance in Istanbul. "Hypocrites! What's so democratic about the theocratic state they're trying to introduce?"
Such attitudes are common among educated Turks, particularly women, who remember the fear that AKP's aggressively Islamist predecessor inspired in them during its stint in power between 1996 and 1998.
"Turkey isn't Iran, and never will be," agrees her friend Burcu Alatas, a secretary. "When I see women dressed from head to toe in black, I feel so ashamed. It's so backward."
She's referring to the Iranian-style robe worn only by a tiny minority of Turkey's most conservative women, women one former prime minister contemptuously described as "looking like bats." While a poll published in the centrist daily Milliyet this May concluded that nearly 70 percent of Turkish women cover their heads, most adopt less austere styles.
In rural Turkey, the most common garment is a veil that hides only the hair. But the secularists' real gripe is the scarf that women pin tightly under their chins. Turkey isn't the only country wrestling with the issue. France, Germany, and other European countries are all trying to reconcile the demands of Muslim minorities with public opinion. But it is the closeness of the perceived Islamic threat that gives the debate here its bitter tinge.
"For me [these scarves are] proof you stand against Atatürk's efforts to pull this country out of the Middle Ages," says Ms. Ertekin. "And they belittle the women who wear them."
Such attitudes irk Leyla Hanioglu, a head scarf-wearing Istanbul dentist who trained in Britain. "How can a country that bans the majority of its women from public service call itself modern?" she asks. "Wearing a head scarf makes me feel good, not belittled. Is that so difficult for these so-called modern Turks to understand?"
"Do they really think," she adds, "that I would become an acceptable democrat if I took to the streets flaunting a blond perm?"
Speaking on the phone from Diyarbakir, the capital of Turkey's socially conservative Kurdish southeast, teacher Necmiye Celik is equally vehement. "You host a party to celebrate the Republic's unity and refuse to allow some people to attend - a contradiction, no?" she says. "For me, the message is clear - Turkey has no space for people like us."
"When my husband went off to do his military service, neither [my mother-in-law] nor I could attend his farewell dinner at the barracks because we wear head scarves," adds her neighbor Semra Capar. "She has given three sons to serve this country. Is she not a loyal citizen?"