How did historian arthur schlesinger, jr., describe the powers that president johnson assumed as he escalated the war in vietnam?

 Schlesinger described it as IMPERIAL PRESIDENCY.

Detail:

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:

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.

the roman army grew in size and became dominant in the mediterranean region.