Japanese aviator’s photograph of the opening assault on Pearl Harbor as torpedoes streak towards Battleship Row and Hickam Airfield burns in the distance. Source: Imperial Japanese Naval Air Service.

“Our hearts are broken, but they are beating, and they are beating stronger than ever. New Yorkers are unified, we will not yield to terrorism.” — Mayor Rudy Giuliani – September 29, 2001 on Saturday Night Live.

“A military man can scarcely pride himself on having ‘smitten a sleeping enemy;’ it is more a matter of shame, simply, for the one smitten. I would rather you made your appraisal after seeing what the enemy does, since it is certain that, angered and outraged, he will soon launch a determined counterattack.” — Admiral Isoruku Yamamoto to a government reporter, 1942.

“We were united, and the outpouring of generosity and compassion reminded us that in times of challenge, we Americans move forward together, as one people.” — President Barack Obama in his Weekly Address, August 27, 2011.

Now nineteen years separated from the September 11, 2001 attacks on the United States, the events in the successive months triggered a new era of geopolitical actions globally revolving around a “Global War on Terror” that involved a myriad of nations brawling with a variety of non-state actors who at least nominally aligned with radical Islamic doctrines.

The imperative of this “War” has only faded in the public eye as state and state-funded actors have become the foremost concern for the world’s leading nations. Another aspect of the attacks that is frequently recalled by those who lived through them is a keen sense of “national unity,” one which is often compared to the reaction by the American people to the December 9, 1941 Pearl Harbor attack by Imperial Japan. The data we have from 2001 also reflects this. In weekly public opinion polling by Gallup before the attacks, George W. Bush’s approval rating leapt from a decent level of popularity (for a US President) at 51% to a peak of 89% the following October, something unheard of outside of times of war. This phenomenon, usually described by lay people as a “moment of national unity” or a rally-around-the-flag event, is called the rally effect by social scientists.

The “rally effect” is defined as the propensity of the general public and domestic political actors to back current leadership during times of crisis. September 11, 2001 is the textbook example of how an action, a terror event, that theoretically should have a psychologically dampening effect (inspiring fear and dissatisfaction with the government) can instead psychologically inspire the targeted polity.

In 1970, political scientist John Mueller first codified the rally effect as a US-centric phenomenon when he labeled it as an international event involving the United States that is “specific, dramatic and sharply focused.” Mueller further identified archetypes for what rally events can occur around, two of which; sudden military intervention and major diplomatic actions (US-Soviet summits for example) persist in their relevance. Political actors and even journalists had already been instinctually aware of the idea for some time, and the term has been adapted to have a perspective that can encompass any polity.

The question of what triggers a rally effect is one of heavy debate: a rational school holds that the public sees a leader proffering a sharp policy of acceptable cost and rallies around them, a realist conception states that the public wants policy that is just. There is also the patriotism school of thought, where rallying behind the president occurs simply because they’re perceived as the avatar of America, and the opinion leader school, which holds that if the political opposition doesn’t sign up for the rally you don’t have one.

Many put the 9/11 Attacks underneath the patriotism rubric, which is also notable for its enduring effect as the Bush administration was able to ride support for the war into the invasion of Iraq. Conversely, unpredictability ensues from how, despite its sudden sharpness and ultimate American victory on the ground, the Tet Offensive provided no such benefit to President Lyndon Johnson, whose Vietnam War policy increasingly embraced an American withdrawal from the war. Whether this was because American’s were “rational” and decided war was unacceptable, or because Johnson’s opposition refused to go along with the war program per the opinion leader school, the unpredictability of the rally effect is well illustrated.

Whichever conception of the rally effect might be true is dependent on what is happening within these diverse schools of thought, illustrating why recapturing that 9/11 moment is in some ways like trying to put lightning in a bottle.