"You don't make peace with your friends, you make peace with your enemies. . . "

I've seen that statement attributed to Desmond Tutu, to Moshe Dayan, and to Mac Maharaj. Whoever said it simply stated a critical truth.

The P-5 + 1 (that's the permanent members of the UN Security Council and Germany, to you and me) have reached an agreement with Iran:

Iran and a group of six nations led by the United States reached a historic accord on Tuesday to significantly limit Tehran’s nuclear ability for more than a decade in return for lifting international oil and financial sanctions.

The deal culminates 20 months of negotiations on an agreement that President Obama had long sought as the biggest diplomatic achievement of his presidency. Whether it portends a new relationship between the United States and Iran — after decades of coups, hostage-taking, terrorism and sanctions — remains a bigger question.

Mr. Obama, in an early morning appearance at the White House that was broadcast live in Iran, began what promised to be an arduous effort to sell the deal to Congress and the American public, saying the agreement is “not built on trust — it is built on verification.”

He made it abundantly clear he would fight to preserve the deal from critics in Congress who are beginning a 60-day review, declaring, “I will veto any legislation that prevents the successful implementation of this deal.”

Almost as soon as the agreement was announced, to cheers in Vienna and on the streets of Tehran, its harshest critics said it would ultimately empower Iran rather than limit its capability. Israel’s prime minister, Benjamin Netanyahu, called it a “historic mistake” that would create a “terrorist nuclear superpower.”

A review of the 109-page text of the agreement, which includes five annexes, showed that the United States preserved — and in some cases extended — the nuclear restrictions it sketched out with Iran in early April in Lausanne, Switzerland.

Yet, it left open areas that are sure to raise fierce objections in Congress. It preserves Iran’s ability to produce as much nuclear fuel as it wishes after year 15 of the agreement, and allows it to conduct research on advanced centrifuges after the eighth year. Moreover, the Iranians won the eventual lifting of an embargo on the import and export of conventional arms and ballistic missiles — a step the departing chairman of the Joint Chiefs of Staff, Gen. Martin E. Dempsey, warned about just last week.

So what to make of the agreement?

First, let's be frank: the USA could refuse to sign the deal, although it's very unclear that the votes are there to override the President's veto. More to the point, what was the option? As the President said:

In an interview Tuesday with Thomas L. Friedman, an Op-Ed columnist with The New York Times, Mr. Obama also answered Mr. Netanyahu and other critics who, he said, would prefer that the Iranians “don’t even have any nuclear capacity.” Mr. Obama said, “But really, what that involves is eliminating the presence of knowledge inside of Iran.” Since that is not realistic, the president added, “The question is, Do we have the kind of inspection regime and safeguards and international consensus whereby it’s not worth it for them to do it? We have accomplished that.”

According to the Times, Secretary of State John Kerry managed to negotiate real inspections with teeth. Indeed, he appears to have obtained a way to reimpose sanctions if Iran doesn't comply:

Mr. Kerry appeared to secure another commitment that was not part of a preliminary agreement negotiated in Lausanne. Iranian officials agreed here on a multiyear ban on designing warheads and conducting tests, including with detonators and nuclear triggers, that would contribute to the design and manufacture of a nuclear weapon. Accusations that Tehran conducted that kind of research in the past led to a standoff with inspectors.

So, it's a knotty one, isn't it. Do we make peace with Iran, whose seizure of 52 hostages in 1979 ended the Carter Era, inaugurated that of Reagan, and led to decades of seething hatred on both sides?

If the deal is workable, do we make peace with our enemies?

Well, we know we don't do it with our friends.