On March 20, 2018, Israel admitted that it bombed Syrian President Bashar Assad’s nuclear reactor in 2007. If Israel attacks Iran’s nuclear sites the latter will respond. Two weeks ago a large-scale joint US-Israeli military exercise took place in Israel, focused on the scenario of an Iranian attack on Israel. Should the United States defend Israel from such a threat? Particularly since the late 1960s there have been close relations between Israel and the US, including at the military level. Yet there is no official military pact between them. The US has given Israel, since 1949, more than $124 billion in military aid. The Israeli military, mostly its air force, has been based on American weapon systems. The concept was that the US provides Israel with weapons but not troops, since Israel relies on its own. American weapons, Israeli blood. According to a recent Gallup poll, 74% of American adults have a favorable view of Israel. This is the highest showing for Israel since 1991. Then, during the 1991 Gulf War, the US deployed Patriot missile defense batteries in Israel to intercept Iraqi long-range surface to surface missiles. It was the first time US forces had been sent to defend Israel directly, although the deployment was very limited in scale and not particularly effective.In March 2018 the US and Israel conducted “Juniper Cobra,” a joint anti-missile drill that has been conducted several times since 2001. The goal of Juniper Cobra 2018 was the defense of Israel from an Iranian missile attack.If a war breaks out between Israel and Iran, US forces will need several days to get to Israel, unless the US knows in advance that hostilities are imminent. For example, if Israel and/or the US decide to attack Iran’s nuclear sites, they would prepare for Iranian retribution.In May 2018 the Trump administration might get out of the Joint Comprehensive Plan of Action (JCPOA), the agreement about Iran’s nuclear program that was signed on July 14, 2015. Although that agreement is between Iran and several world powers, not only the US, without the US it might fall apart. In such a scenario Iran might rush to produce a nuclear weapon and the military option might be the only way to stop it.As long as Iran does not have nuclear weapons, the main threat to Israel is Iran’s proxy in Lebanon, Hezbollah, a non-state organization that possesses up to 150,000 rockets, capable of hitting any target in Israel. Compared to Hezbollah, the danger to Israel from Iranian missiles is not that serious, since Iran has only several hundred missiles capable of reaching Israel. In that sense Israel does not require so much US assistance, let alone US troops risking their lives for it. It is better for Israel to ask its American patron to help in the traditional way, i.e. by delivering ammunition, spare parts, etc., to the IDF and backing Israel in the international arena.During a war US forces might play a purely defensive role, by intercepting Iranian missiles for example, yet Iran might see that as an aggressive act and retaliate against US forces in the Persian Gulf. That could ignite a war between Iran and the US.In light of all the above, the conclusion is clear: Israel should rely on its own forces, as it always has. (The exception, besides the 1991 war, was in 1956 when, following a secret pact, Israel joined Britain and France in attacking Egypt. French forces were deployed in Israel before the war, to protect its skies from Egyptian bombers. During the war there were only two attempts by Egypt to bomb Israel, which failed.) Finally, while US and Israeli troops strove in the recent joint exercise to create common doctrine, language, etc., despite those efforts there remain differences between the two militaries that can make it difficult for them to operate together.Israel has about 10 Iron Dome missile defense batteries, but may need up to 20. Each one costs about $60 to $80 million, and each missile costs up to $50,000. The US can help defray those costs, having already allocating huge budgets to supporting the development of the Iron Dome. Yet Israel must consider other options. Besides the high cost, even if Israel pays for it alone a purely defensive strategy will make Israel look weak. Israel should make it clear that since it does not have enough Iron Dome batteries to protect itself, then its response will be severe. Israel should also consider a preemptive strike, if there is no other choice.All in all Israel, certainly at the military level, is quite powerful and its economy is doing relatively well. Therefore Israel should approach the US to ask for significant defense-related funding only when and if it is truly necessary. Israel must in particular weigh very carefully any request for direct US military assistance, which should be viewed as an option of last resort.The author is an analyst of Israel’s national security, and used to work for the IDF.