Note the senator’s clear premise: It is for the president to “pick” between war involving millions of deaths, and peace. Congress, its arthritic knees creaky from decades of genuflections at the altar of presidential power, will be a gimpy spectator.

The OLC says it has “well over 100” episodes that support its contention that for 230 years presidents have unilaterally employed force in episodes short of “sustained, full-scale conflict with another nation.” Note well: “Sustained.” “Full-scale.” “With another nation.”

The OLC notes that even the 1973 War Powers Resolution, by which Congress attempted to circumscribe presidential war-making discretion, allows presidents to introduce U.S. forces into hostilities for at least 60 days without congressional authorization. Still, the OLC acknowledges that presidents must “resort to Congress” for approval of hostilities “which reach a certain scale,” involving U.S. troops in “significant risk over a substantial period.” “Certain” scale. “Significant” risk. “Substantial” period. There can be “substantial” deployments (e.g., two years enforcing a no-fly zone, and 20,000 ground troops, in Bosnia) and engagements more violent than April’s Syria episode (e.g., the U.S.-led 2011 air campaign in Libya lasting more than a week and involving more than 600 missiles and precision-guided munitions) without “war in the constitutional sense.”