By a vote of 71 to 26, the US Senate on Wednesday approved the New START treaty that aims to reduce the US and Russian nuclear arms arsenals and reopen them to mutual inspections.

Thirteen Republican senators joined a unanimous Democratic bloc of 57 to surpass the 66 vote minimum required to ratify the treaty, which was signed by President Obama and Russian President Dmitry Medvedev in April.

The treaty calls for a reduction of about one third in both the US and Russian nuclear stockpiles over the course of seven years, down to 1,550 strategic warheads on each side, and it opens up the arsenals to new inspections by officials from both countries. The US and Russia share about 95 percent of the world’s total nuclear weaponry.

The Obama administration’s defense of the treaty makes clear that the US deems the agreement necessary not to secure peace, but to better prepare for war. The treaty aims to smooth relations with Russia, whose support is considered indispensable to the US effort to subjugate Afghanistan and make way for operations against Iran. Strategists also hope to neutralize Russia in the growing US-China conflict.

“Without a new treaty, we’ll risk turning back the progress we’ve made in our relationship with Russia, which is essential to enforce strong sanctions against Iran, secure vulnerable nuclear materials from terrorists and resupply our troops in Afghanistan,” Obama said in his weekly radio address Saturday.

Other backers of the treaty noted that Washington would still have an overwhelming nuclear superiority over any potential rival. The treaty would still give the US “enough nuclear warheads to blow any attacker to kingdom come,” said Republican Senator Lamar Alexander of Tennessee in explaining his vote in favor of the agreement.

The military also wants a resumption of mutual inspections as stipulated by the treaty, explaining that if the US has to spy on Russia to gather basic data about its nuclear arsenal, the effort will divert resources from operations targeting other countries—for example, satellites that are currently used to monitor the activities of insurgents in Afghanistan, Pakistan, and Iraq. Mutual inspections expired in December of 2009 with the expiration of the START I treaty, which had been concluded between President George H.W. Bush and Soviet Premier Mikhail Gorbachev just months before the collapse of the Soviet Union in 1991.

Treaty ratification was a victory for the military and foreign policy establishment, which overwhelmingly favored the agreement. In a letter to the Senate issued on Monday, the top US military officer, Chairman of the Joint Chiefs of Staff Adm. Mike Mullen, called the treaty “vital to US national interests” and said it “has the full support of your uniformed military [who] all support its ratification.”

“The Joint Chiefs and I are confident that the treaty does not in any way constrain our ability to pursue robust missile defenses,” Mullen wrote in the letter, which was read aloud to the Senate by John Kerry, chairman of the Committee on Foreign Relations. Mullen insisted that the treaty would not interfere with the development of the conventional prompt global strike (CPGS) system, which will allow the delivery of large-scale conventional weapons on intercontinental ballistic missiles and other weapons platforms covered under New START.

“Importantly, the New START treaty allows the United States not only to deploy CPGS systems, but also to continue any and all research, development, testing and evaluation of such concepts and systems,” Mullen wrote.

In promoting the treaty, Mullen and Secretary of Defense Robert Gates emphasized practical military considerations, especially the “flexibility” the treaty would give the military by partially freeing it up from what remains, at least militarily, its closest rival.

Mullen’s invocation of military support for the treaty gained the support of several Republicans. “We all talk on our side of the aisle about listening to our military leaders,” said Sen. Bob Corker of Tennessee. “And if you look from A to Z, there’s a lot of support for this treaty.”

Leading establishment Republicans such as George H. W. Bush and former secretaries of state George Shultz, James Baker, Condoleezza Rice and Henry Kissinger had called on senators to support the treaty.

The Obama administration lobbied heavily for passage, sending both Vice President Joseph Biden and Secretary of State Hillary Clinton to Capitol Hill on Tuesday to help secure cloture, or the closing down of debate in order to proceed to the vote. This passed 67 to 28, with 11 Republicans joining a unanimous Democratic caucus.

Defeat of the treaty would have been a debacle for US foreign policy. “Champions of the measure believe approval will avoid a ‘devastating’ blow to US prestige on the world stage and end Mr. Obama’s year on a victorious note,” the Financial Times noted. According to the Washington Post, “Defeat would have severely damaged Obama’s global standing, hampering his ability to negotiate other treaties.”

The fact that a large majority of Senate Republicans voted against the agreement underscored the erosion of what had been a longstanding tradition, in which international treaties negotiated by the White House were generally supported by both parties. Senate Minority Leader Mitch McConnell of Kentucky opposed the agreement and was joined in opposition by the Senate Republicans’ second-ranking member and its lead negotiator on the treaty, Jon Kyl of Arizona.

All of the likely candidates for the Republican nomination for the presidency in 2012 also opposed the treaty, including former Alaska Governor Sarah Palin, former Minnesota Governor Tim Pawlenty, former Massachusetts Governor Mitt Romney, and former Speaker of the House Newt Gingrich.

Republican opposition to the treaty focused on the document’s preamble, which refers to the “interrelationship between offensive and defensive strategic weapons.” Republican opponents claimed this language could interfere with the creation of a US missile defense shield in Europe, which is opposed by Moscow. Republicans attempted to scuttle the treaty by introducing amendments, one of which would have required Moscow to hand over US-made military hardware seized as a result of Russia’s 2008 war with Georgia.

In response to Republican concerns, Obama issued a pledge to proceed with the four-phase development of a nuclear shield for Europe.

New START’s limitation of the US and Russia to a combined 3,100 warheads will still provide more than enough explosive power and radiation to destroy the world and its inhabitants. One US B53 nuclear bomb delivers an explosive force equivalent to 600 of the atomic bombs used to incinerate Hiroshima at the end of World War II.