Contra the unilluminating commentary from Bret Stephens in the Wall Street Journal, it is difficult to imagine a vigorous Republican “isolationism” worthy of the name that includes John Bolton. The most energetic of our foreign-affairs hawks are a little like the most energetic Keynesians: In their minds, it’s always 1933.

Mr. Stephens believes that the relevant historical precedent for this moment in conservative foreign-policy thinking is the reaction of Robert Taft to the rise of Adolf Hitler:

Taft couldn’t understand this when it came to the dictators of his day. Neither does Mr. Paul when it comes to the dictators of today. The junior senator from Kentucky may not know it yet, but, intellectually speaking, he’s already yesterday’s man. Republicans follow him at their peril.

Bashar Assad is not Adolf Hitler, and his Syria is not Nazi Germany. Bashar Assad is not Nikita Khrushchev, and his Syria is not the Soviet Union. Comparisons between Assad and the great dictators of the 20th century are not very instructive. If we look at what Assad actually is and at what is in fact at stake in this conflict, then our conclusions are bound to be rather different. Analogy goes only so far.

But strangely, Mr. Stephens is vexed at the prospect that we might ask the question of what exactly is at stake in this conflict. He sneers at Senator Rand Paul for saying the following: “The war in Syria has no clear national-security connection to the United States and victory by either side will not necessarily bring into power people friendly to the United States.”

“What’s in it for us?” is the first question that should be asked about any military conflict — not because it is always the most important question, but because the failure to give a convincing answer to it constitutes a bright flashing neon sign reading “Caution.” Senator Paul argues that the conflict in Syria has “no clear national-security connection to the United States.” If he is incorrect, then that connection should be made obvious. If he is correct, then proponents of action in Syria have before them the difficult but not impossible task of explaining precisely why we should proceed regardless.

None of that implies a resurrection of Senator Taft.

In the September 2 issue of National Review, I have an essay arguing that conservatives should reconsider their assessment of President Dwight E. Eisenhower. It seems to me that conservative hesitation regarding Syria is much more akin to President Eisenhower’s aversion to “brushfire wars” than to Senator Taft’s ideological isolationism. Our national failure to achieve our desired outcomes in Afghanistan and Iraq has in fact eroded the moral and political infrastructure needed to support sustained military conflict when it is necessary to do so. The contemplated action in Syria is not a nation-building campaign on the scale of Iraq or Afghanistan, but it is very likely also to result in our failing to achieve our national objectives therein, since we do not have any. The unarticulated mission of the Syria war is to demonstrate to the world that the United States under the leadership of Barack Obama is something other than a feckless menace to its own global interests and to those of its allies. That mission is not achievable.

Senator Taft’s was not the only unreasonable position that President Eisenhower had to negotiate. On the other hand, he had many conservatives who sought a policy of maximum confrontation with Communism, the partisans of which advised, among other things, the use of nuclear weapons during the Dien Bien Phu episode and during the Formosa Straits crisis. It was far from an established assumption at the time that nuclear weapons would not be routinely deployed during combat. Ironically, the intellectual heirs of those who recommended the use of nuclear weapons in the 1950s are today arguing for a strike against Syria in the name of upholding global norms against the use of mere chemical weapons.

If at the end of this debate we have a standard for the use of military force that is incrementally more oriented toward to the pursuit of actual U.S. national-security interests and a Congress that has reclaimed some of the war-making authority that it has unwisely ceded to the executive over the years, then the nation will have reason to thanks Senator Paul and Representative Justin Amash. We will also have a diminished president and a dangerously degraded credibility in world affairs, which is yet another price to be paid for having twice put Barack Obama into an office for which he is manifestly under-equipped.