Two American flags were replaced with white flags atop the Brooklyn Bridge on Tuesday. Authorities don't believe the switch was connected to terrorism. (Reuters)

On July 22 at around 3:30 a.m., unknown parties climbed atop the Brooklyn Bridge and replaced the American flags flying there with white ones.

More specifically: The flags were Old Glories treated with bleach.

Authorities could only shrug.

“We’re lucky they just put a flag up there — and not a bomb,” a law enforcement source told the New York Post. “It could have been terrible. Who knows how much damage it could have done. It’s an embarrassment.”

“There’s no particular nexus to terrorism or politics,” NYPD anti-terrorism chief John Miller said at a press conference. “It might be some kind of art project or statement. But we are not sure what that statement is.”

“Isn’t there a better way to express yourself?” Nick Krevatas, a cigar-puffing bridge painter, told the New York Post. “Couldn’t they have used social media?”

When stogie-wielding municipal workers can’t interpret your political message sans Twitter, you’re in trouble. What the deuce could those darned flags have meant?

Well, white flags are traditionally associated with surrender. Such flags were raised in China and Rome millenia ago, perhaps inspiring the Gothamist headline: “Surrender, Brooklyn.”

But what is Brooklyn supposed to surrender to? The forces of gentrification? Bike lanes? Bands that all sound the same?

Then again, the white flag doesn’t exactly mean “surrender.” In the Geneva Convention, such banners are “truce flags” meant for “inviting the belligerents to conclude truces to permit the removal of wounded and sick from a besieged area, and to allow medical personnel and equipment to be sent to that area.” So the flag could be a call for a truce — perhaps between Israel and Gaza, as BKMag speculated.

But the white flag also has some pretty distasteful associations.

The second flag of the Confederacy incorporated the familiar stars and bars on a plain white background. The “stainless banner” didn’t go over well with Johnny Rebs — when Minie balls flew, the flag was often mistaken for a truce flag, leading to a redesign in the rebellion’s dying days. As the New Jersey company Annin Flagmakers explained on its Web site: “The ‘Bloody Stripe’ was added to differentiate the flag from the white flag of surrender and prevent further confusion on the battlefield.”

Perhaps more relevant in our current political climate: The white standard was also flown by the Umayyad dynasty, a caliphate born after the death of the prophet Muhammad. But anti-Muslim conspiracy theorists should know that the Umayyads weren’t necessarily religious fanatics. As per Britannica, this was  “the first great Muslim dynasty to rule the empire … sometimes referred to as the Arab kingdom (reflecting traditional Muslim disapproval of the secular nature of the Umayyad state).”

Another remote possibility: White Flag is a punk parody band that takes its name from the legendary L.A. hardcore group Black Flag — but anyone old enough to remember that is probably not spry enough to climb the Brooklyn Bridge.