In the early months after the 9/11 terror attacks, America's visceral reaction was to gird for a relentless, whatever-it-takes quest to punish those responsible and prevent any recurrences.
To a striking extent, those goals have been achieved. Yet over the years, Americans have also learned about trade-offs, about decisions and practices that placed national security on a higher plane than civil liberties and, in the view of some, above the rule of law.
It's by no means the first time in U.S. history that security concerns spawned tactics that, when brought to light, troubled Americans. But the past decade has been notable, even in historical context, for the scope and durability of boundary-pushing practices.
Abroad, there were secret prisons and renditions of terror suspects, the use of waterboarding and other interrogation techniques that critics denounced as torture, and the egregious abuse of detainees by U.S. military personnel at Iraq's Abu Ghraib prison and elsewhere.
At home, there has been widespread warrantless wiretapping authorized by the National Security Agency and the issuance of more than 200,000 national security letters ordering an array of Americans - including business owners and librarians - to turn over confidential records.