There is an interesting story in today's Wall Street Journal describing how Obama backed Israel's Iron Dome missile defense system despite opposition from the Pentagon. Under Bush, funding for Iron Dome had been refused, apparently because the Pentagon believed it was unfeasible - they wanted Israel to adopt the US-based Phalanx system instead.
The story also describes how the system got developed so quickly despite opposition within the Israeli defense establishment - so many bureaucratic corners and red tape got cut that if Iron Dome had not worked many heads would have rolled.
The WSJ article might be behind a paywall, so I'll quote a few selected extracts that emphasize the role Obama played.
Israel's Iron Dome Defense Battled to Get Off Ground
Iron Dome got a significant boost soon after President Obama came to office in 2009. Mr. Obama visited Sderot as a presidential candidate and told his aides to find a way to help boost Israel's defenses from the makeshift rockets, his aides said, although defense officials at the time still doubted Iron Dome was the way.
As president, Mr. Obama tapped Colin Kahl to run the Pentagon office overseeing U.S. military policy in the Middle East. Mr. Kahl found the Iron Dome request on his desk, decided to take another look and had what he later described as a light-bulb moment. "Ding, ding, ding. It just made sense," Mr. Kahl said.
In 2009, the peace process topped Mr. Obama's foreign-policy agenda. But the administration's call for a freeze in Jewish settlement growth badly strained ties with Israel's right-wing prime minister, Benjamin Netanyahu. Top Obama administration advisers saw supporting Iron Dome as a chance to shore up U.S.-Israel security relations and balance some of the political strains.
At the direction of a White House working group headed by then-National Security Council senior director Dan Shapiro (who today is the U.S. ambassador to Israel), the Pentagon sent a team of missile-defense experts to Israel in September 2009 to re-evaluate Iron Dome. The decision raised eyebrows in some Pentagon circles. Iron Dome was still seen as a rival to the Phalanx system, and previous assessment teams had deemed Iron Dome inferior.
In its final report, presented to the White House in October, the team declared Iron Dome a success, and in many respects, superior to Phalanx. Tests showed it was hitting 80% of the targets, up from the low teens in the earlier U.S. assessment. "They came in and basically said, 'This looks much more promising…than our system,' " said Dennis Ross, who at the time was one of Mr. Obama's top Middle East advisers.
That summer, Mr. Kahl's office drafted a policy paper recommending that the administration support the Israeli request for roughly $200 million in Iron Dome funding.
Earlier in the process, the Bush Pentagon had refused to back the proposed system:
Israel's Defense Ministry approached the U.S. administration of President George W. Bush with a request for hundreds of millions of dollars for the system. The reception at the Pentagon was frosty, according to current and former U.S. defense officials.
...
Rafael's Mr. Drucker recalls an even harsher U.S. response. He said the U.S. team told them: "This is something that cannot be done."
Some U.S. military officials argued that Israel should instead consider using a version of the U.S.'s Vulcan Phalanx system, which the Army was deploying in Iraq to try to shoot down incoming rockets, current and former defense officials say. Gen. Gold's team had already considered and dismissed the Phalanx system.
It should be understood by everyone that the success of Iron Dome does not imply that an anti-ICBM system is feasible. They are very different technical problems - an ICBM is moving perhaps 30 times as fast and can easily deploy decoys. Iron Dome has a very limited range - its breakthrough from a technological perspective is how quickly it can react to short-range rockets and artillery and how (comparatively) cheap each interceptor missile is.
From a political perspective, Obama quickly grasped that Iron Dome would be a stabilizing factor. Indeed, it has been credited for preventing an Israeli ground invasion of Gaza.
Obama also understands that an ICBM defense system would be destabilizing as it would provoke counter-measures from Russia.