Researching the Preparedness Day Parade bombing, I realize that this story is truly larger than just the parade itself.  For instance, what was the initial reason for the parade?

The history of the Preparedness movement is fascinating in itself.  It pits former President Theodore Roosevelt against President Woodrow Wilson.  Over the course of several years, Roosevelt publicly criticized and disparaged President Wilson regarding the state of American military readiness.  An ongoing Mexican civil war threatened to spill over into America through the raids on American soil throughout the American Southwest and killings of Americans in Mexico by General José Doroteo Arango Arámbula, better known as Pancho Villa.  The Mexican civil war coupled with the Great War in Europe and the sinking of merchant ships all across the Atlantic Ocean led many Americans to demand a heightened state of military preparedness should another nation present a present danger to American sovereignty.

Former President Roosevelt takes very pointed attacks at President Wilson and others not willing to increase American military might, referring to "professional pacifists" as moralists not willing to take a stand against immoral behavior by others.  The press apparently had a field day whenever Roosevelt made a speech promoting preparedness, as his speeches made headlines noting his criticism of Wilson.