Donald Trump's campaign has been short on specifics, but that changed earlier this month when he gave a speech that provided some examples of what his proposed defense buildup would entail.

Before we look at the costs of the Trump buildup, it's worth considering whether we need a buildup at all. As my colleague Stephen Miles of Win Without War and I pointed out in a recent piece, the Obama administration has spent more on the military than George Bush did, and current levels exceed the peak years of the Reagan administration. This is a massive amount of funding, by any measure. Spent wisely, it is more than enough to provide a robust defense for the United States and its allies.

As for Mr. Trump, although he asserted that he was opposed to "toppling regimes" and that his administration would "stress diplomacy, not destruction," he still called for increasing spending on virtually every aspect of the U.S. military. He called for increasing the Navy from its current goal of 308 ships to 350; adding 60,000 troops to the Army; increasing the Marines by over one-third, from 23 to 36 battalions; buying scores of additional combat planes for the Air Force; and sharply increasing spending on missile defense, which has received hundreds of billions of dollars over the years with little to show for it.

Todd Harrison of the Center for Strategic and International Studies notes that it's hard to put a precise figure on the cost of the Trump plan:

"Trump's defense plan does not provide enough detail to accurately estimate what he would spend on defense. For example, the cost of his proposed 350-ship Navy depends to a great extent on what kind of ships he wants to build. Aircraft carriers cost upward of $12 billion, while much smaller and less capable Littoral Combat Ships cost around $600 million."

However, Harrison also notes that there is a way to get a rough idea of what the Trump plan might cost:

"What we do know is that Trump has been drawing many of his defense proposals from the National Defense Panel and the Heritage Foundation. Both of these organizations have advocated for returning the defense budget to the levels proposed in the FY 2012 budget request (the so-called Gates budget). Without any other details from the Trump campaign, I think this is a good ballpark estimate for what Trump is aiming for in terms of the defense budget. The FY 2012 request is about $800-900B higher over ten years than the most recent president's budget request."

So if Trump is not going to engage in large-scale interventions akin to those in Iraq and Afghanistan, what is all of this money for? In brief, Trump's theory seems to be that if the United States spends enough on its military, other countries will be "scared straight" and behave themselves. This is magical thinking. The world doesn't work that way.

Whether in Russia, Asia, the Middle East, Africa, or Latin America, countries and movements will pursue their interests regardless of how much money the United States decides to throw at the Pentagon. The challenge is to create incentives for countries and factions to cooperate rather than fight. This may on occasion involve the use or threat of use of military force, but for the most part it requires smart diplomacy and a recognition of mutual interests.

The Iran nuclear deal is a good example of what can be achieved through patient negotiation. As demonstrated in a compendium of analyses of the deal put together by the Ploughshares Fund on the one-year anniversary of the Iran agreement, the deal is working. It has already dramatically reduced Iran's nuclear capabilities, and it headed off the threat of war that was implicitly or explicitly supported by many opponents of the agreement.

One of the secrets of the deal's success was the decision to bring a significant number of interested parties to the table, from the U.K., France, and Germany to the United States, Russia, and China. The inclusion of Russia and China, which have significant disputes with the United States and European powers on other issues, is a good example of how mutual interests on a particular issue can bring together potential adversaries to achieve concrete gains in security for all. The president and his allies must be vigorously supported in their defense of this crucial agreement against its critics in Congress. It should be noted that Mr. Trump roundly and inaccurately denounced the Iran agreement in his defense speech.

In a future column I will look at the potential costs of Hillary Clinton's defense plans, based on her public statements and the proposals put forward by some of her key advisors and potential cabinet members. Like Mr. Trump, she has called for lifting the caps on Pentagon spending imposed by the Budget Control Act of 2011, which means the trajectory of Pentagon spending in a Clinton administration is likely to go up as well, although probably not to the stratospheric levels proposed by Mr. Trump.

Critics of throwing more money at the Pentagon at the expense of more effective approaches to security need to be heard and highlighted in the media in the stretch run of the presidential campaign, so that 2017 doesn't mark the start of an unnecessary Pentagon buildup of major proportions.