In a rare and very open speech he delivered on Christmas Day, IDF Chief of Staff Aviv Kochavi outlined Israel’s military challenges for the coming year. It was the first time in many years Israeli military brass joined Israel’s political leaders in identifying Iran’s regional aggression (as opposed to its proxies) as a top concern.In a surprising turn of events, two days later an Iranian proxy struck a US base in Kirkuk and killed an American contractor. The US struck back at the Shi’ite militia, Kataib Hezbollah, prompting Iran to orchestrate a siege of the embassy in Baghdad. A few days later, the United States struck down the head of Iran’s Quds Force, Qassem Soleimani, in a pinpoint drone strike. The Iranian regime responded by striking Iraqi bases housing American servicemen on Tuesday night. US-Iran tensions continue to rise. Viewed from afar, it appears that Israel and the United States are fighting the same battle. But upon closer scrutiny, the two countries are dealing with the challenge of Iran in different ways.Both governments see the conventional threat posed by Iran and its proxies as a dangerous one. As US President Donald Trump and Prime Minister Benjamin Netanyahu have both charged, the international community elected to ignore the conventional threat for several pivotal years, focusing instead on the questionable achievements of the deeply-flawed 2015 Iran nuclear deal, which enriched the regime and offered sunsets on the nuclear restrictions. The Obama administration even enlisted some of Iran’s more dangerous proxies in the fight against the Islamic State. During that time, Iran developed new and more formidable capabilities to hurt the US and its allies through attacks on Middle East oil installations, harassing vessels in the Strait of Hormuz, propping up the murderous Assad regime in Syria, and backing terrorists groups like Hezbollah in Lebanon, Hamas in Gaza or the Houthis in Yemen.Another key area of concern is the nuclear file. Iran’s leaders declared in May their intent to return to more aggressive nuclear activities after Trump withdrew from the deal the previous year. In July, the Iranians began to stockpile more uranium, and they also began to enrich it above the 3.67% allowed (today it’s at 4.5%). The regime began to engage in nuclear activity at the facility known as Arak. Then, in September, the Islamic Republic began to operate advanced centrifuges at Natanz, a nuclear facility in central Iran. In November, the regime began to enrich uranium in Fordow, the previously secret facility built under a mountain, first exposed in 2009.The end result: Iran has crossed the threshold on low-enriched uranium, shortening significantly the time to produce enough fissile material for a nuclear device.The US intends to keep Iran in line with tough sanctions, imposed mostly on a unilateral basis. Finding willing international partners to constrain Iran has not been easy, but the US Treasury and the US dollar dominate the international financial system Even countries that don’t want to cooperate are reluctantly falling in line.In the meantime, the International Atomic Energy Agency (IAEA) is still working to resolve issues relating to Iran’s nuclear activities, especially the Comprehensive Safeguards Agreement violations exposed by documents that Israel captured in a raid on an Iranian nuclear warehouse in 2018. Iran’s noncompliance was firmly established after several visits by IAEA inspectors to the sites exposed by those documents.The top American priority is to prevent Iran from getting a nuclear bomb, and to defend American assets in the region. But the policy is also predicated on prompting the Iranian regime to change. Secretary of State Mike Pompeo delineated 12 requirements that Iran must meet to demonstrate that it is a “normal country.” These range from halting terrorism sponsorship abroad to other destabilizing behavior around the Middle East.THE SOLEIMANI strike signaled a potential change in policy. But it’s entirely unclear whether Trump is committed to punishing Iran for similar or even lesser attacks on American interests in the future. The president recently dispatched more than 3,000 additional troops to the region, and further threatened to strike 52 targets across Iran should the regime cross his red line. But the president’s isolationist tendencies, coupled with congressional demands for authorizing any new conflict in the Middle East, could impede a sustained US conflict with the Islamic Republic.Israel, by contrast, is already engaged in one. The Jewish state vowed to use all available means to halt Iran’s nuclear program. The Israelis are also on a continuous hunt for precision-guided munitions that Iran seeks to supply to its proxies. As a result, the destruction of sites in Iranian-controlled territory across the Middle East, particularly in Syria and Iraq, is a regular occurrence. Israel has also eradicated cadres of Iranian proxies when they have drawn too close to the Israeli border or when they were believed to pose a threat (these strikes may have actually shown Trump how limited operations can be successful against Iran).In the meantime, Israel has also been forced contend with the immediate threats posed by Hezbollah in Lebanon and Hamas in Gaza. Both are terrorist groups that were armed, trained and funded by Soleimani’s war machine.The “war between wars” continues to escalate between Israel and the Iranians. Elements of Israel’s new National Security Strategy delineate the ways in which Israel could up the ante. For one, the Israelis have vowed to strike at not just the perpetrators of attacks, but also the masterminds and others involved in acts of violence perpetrated against them. Israel has also made it clear that it will not shy away from striking at an enemy’s host country and its critical infrastructure. In other words, Israel has put Iran on notice in ways that until Trump’s recent warning the US could not fathom.Thus, while the recent showdown between the US and Iran may have drawn the two efforts closer, Israel and the US appear to be battling Iranian advances on different fronts and in disparate ways. Israel, in fact, has remained remarkably quiet in the aftermath of the Soleimani assassination.Still, both countries can continue to benefit from one another in the spirit of an alliance that has benefited both sides for decades. This includes areas like intelligence, cyber and hi-tech weapons, such as drones and artificial intelligence. Both countries’ commitment to multi-layered missile defense, through systems developed jointly and independently, is another area of cooperation that could prove crucial if Iran chooses to escalate. The recent attacks on US bases in Iraq only underscore how Iron Dome or David’s Sling could help ensure the safety of American troops on the battlefield.One potential area of friction in recent months has stemmed from rumors of diplomacy between Trump and Iranian President Hassan Rouhani. For Israel, the concern was the potential for a deal that did not account for the entirety of the Iranian threat. However, after the Iran-backed assaults on American assets and the subsequent US reprisal, the possibility of negotiation seems remote. To be clear, Trump is still calling for renegotiations, but a breakthrough is unlikely while the US maintains its maximum pressure campaign and continues to warn of additional military force.With the Iranians on their back foot (at least for now), there could be opportunities for collaboration. But Israel and the United States can be expected to continue to handle the Iranian challenge in their own ways.Brig.-Gen. (res.) Prof. Jacob Nagel is a visiting professor at the Technion Faculty of Aerospace Engineering and a senior visiting fellow at Foundation for Defense of Democracies. He previously served as the head of Israel’s National Security Council and as Prime Minister Benjamin Netanyahu’s acting national security advisor. Jonathan Schanzer, a former terrorism finance analyst at the US Treasury, is senior vice president for research at Foundation for Defense of Democracies.