Americans mark the 13th anniversary of the 9/11 terrorist attacks against the backdrop of last night’s on-the-offensive ISIS address by President Obama.

Thirteen. When today’s seniors at Everett High School fumbled in kindergarten, panic flickered on a screen.

History takes years to come into focus.

That week in September, Gov. Gary Locke reassured Washingtonians that the Hanford Nuclear Reservation and the Columbia and Snake River dams were secure. Secure? After 9/11, we could suddenly conjure worst-case images. Fear migrated from the ruins of the World Trade Center to Naval Station Everett.

This was no ordinary attack, presaging no ordinary war. In his 2014 documentary “The Unknown Known,” Academy Award-winning filmmaker Errol Morris asks former Secretary of Defense Donald Rumsfeld about Dora Farms. That’s the forgettable place in Iraq where the U.S. tried but failed to kill Saddam Hussein prior to the 2003 invasion. Would Hussein’s death have averted war?

The Islamic State emerged from al Qaida in Iraq, which didn’t exist before the 2003 invasion. Al Qaida sprang from the Mujahideen who battled the Soviets after its 1979 invasion of Afghanistan and who were armed by the United States. Unintended consequences writ large.

On Sept. 16, just five days after the horror of 9/11, Vice President Dick Cheney told Tim Russert on “Meet the Press,“ “We also have to work, though, sort of the dark side, if you will. We’ve got to spend time in the shadows in the intelligence world. A lot of what needs to be done here will have to be done quietly, without any discussion, using sources and methods that are available to our intelligence agencies, if we’re going to be successful. That’s the world these folks operate in, and so it’s going to be vital for us to use any means at our disposal, basically, to achieve our objective.”

For the George W. Bush Administration, the dark side included waterboarding, extraordinary rendition of prisoners to countries open to torture, and a twisting of the rule of law through the extrajudicial detention of enemy combatants at Guantanamo Bay, Cuba. In 2009, President Obama signed an executive order banning the use of torture, but the United States continues to navigate the dark side through drone warfare and covert ops.

For many, the ends justify the means. We live in a dangerous world.

How will last night’s announcement of a broad coalition to destroy ISIS be viewed through history’s lens? Like 9/11, like so much of history, the lessons take generations to settle.