Good question. During the Phil. Convention of 1787 this issue was framed in regard to executive power. Make war implied that the president alone could send troops into conflict without congressional approval, something the King of Great Britain, for example, could legally do. Declare was a much more restrictive term and pulled the power away from the executive office. Hamilton argued as much in Federalist No. 69. Congress has punted on the issue since World War II, and it could be argued that their “authorization” agreements are little more than rubber stamps for executive usurpation of constitutional war powers. The founding generation wanted the president to be able to repel sudden attacks, for example an invasion of the American mainland, but actually deploying troops and bringing America to a war footing required a formal declaration. Congress cannot constitutionally give the president power it alone has, nor can the president constitutionally take delegated powers from congress without an amendment. There were fears the president would eventually assume this power, but proponents of the Constitution in 1787 and 1788 assured Americans in all the States that the power of the sword would be safeguarded by the congress. We can now see that the opponents of the Constitution were correct.