What did historian arthur schlesinger, jr., mean by the term "imperial presidency"?

Schlesinger was referring to the tendency for presidents to increase their power beyond normal consitutional limits in times of war.

Arthur Schlesinger's 1973 book, The Imperial Presidency, detailed how wartime situations tended to allow presidents to accrue to themselves larger powers than granted by the US Constitution.  President Johnson's actions in obtaining the Tonkin Gulf Resolution from Congress in 1964 is an example, giving the President extremely wide leeway in use of the military, which escalated US involvement in Vietnam.  But that's only one example, and Schlesinger's argument looked at how presidential powers, particularly in foreign affairs, tended to be increased by all presidents in wartime.

In an article that Schlesinger wrote during the Reagan presidency, he quoted a Civil War era example:

“We elect a king every four years,” Secretary of State William H. Seward told a London Times correspondent during the Civil War, “and give him absolute power within certain limits, which after all he can interpret for himself.”

In that same article, Schlesinger noted:  "Presidents Truman, Johnson, Nixon, and Reagan thereafter assumed that the power to send troops into combat is an inherent right of the presidency and does not require congressional authorization."

Citation:  "The Imperial Temptation," by Arthur Schlesinger, The New Republic, March 14, 1987.

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