Iran’s military entrenchment in Iraq poses a threat to Israel, defense officials say.

Iran began bolstering its presence in Iraq after Israel stepped up attacks on Iranian targets in Syria and Syrian President Bashar Assad regained control over most of his country. Israel’s efforts to thwart Iran’s attempts to bring sophisticated weaponry and air and naval forces into Syria led Tehran to revert to its old method of relying on local militias, which is harder for Israel to counter.

Israel’s intelligence assessment for 2019 states that despite Iran’s difficulties in entrenching itself militarily in Syria, it hasn’t given up on its ambition “to create regional hegemony for itself via alliances spreading from Iran through Iraq and Syria to Lebanon.” Nevertheless, the assessment continued: “Iran has been forced to recalculate the way it tries to realize its regional vision. This recalculation led Iran to realize that the domestic and international situation in Iraq created better opportunities for it to prepare its regional plans.”

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Israeli defense officials say Iran has shifted the bulk of its deployment of missile systems outside the country to Iraq, which is harder for Israel to attack than Syria was. The latest airstrikes on Iraq, which the London-based paper Asharq Al-Awsat attributed to Israel on Tuesday, were aimed at such missile systems.

According to Israeli intelligence, Iran is currently providing Iraqi militias with missiles that have ranges of 200 to 700 kilometers and are capable of hitting anywhere in Israel. These missiles are more accurate than the ones in Hezbollah’s arsenal. Iran may use them either to hit Israel directly from northern Iraq or to transfer them as needed to Syria and Lebanon.

Iran’s regional deployment is largely based on missiles because it doesn’t think its aerial and ground forces are capable of standing up to Western armies. Consequently, it has focused on improving both the range and accuracy of its missiles in recent years.

According to media reports, the latest airstrikes attributed to Israel took place in northwestern Iraq. They targeted weapons storehouses and missiles at bases where Iranian advisers were present.

Two weeks ago, the media reported a drone strike in Iraq that killed members of the Iranian Revolutionary Guards and Hezbollah. Foreign media reports said the target that time was a base where missiles destined for Iranian-backed militias in Iraq were being stored.

Foreign media have also reported several other attacks on Iraq, some of which were attributed to Israel.

So far, however, Israel has kept mum about all these attacks, aside from a video clip published by the ruling Likud party that showed Prime Minister Benjamin Netanyahu in an old speech to the United Nations vowing to act against Iran anywhere, including in Iraq. This clip, reposted three days after the attack on the base where Iranian forces were killed, could be seen as a hint that Israel was behind that strike.

But Israel has much less freedom of action in Iraq than in Syria, because while it has the capability to strike Iraq, doing so could create problems with the United States administration.

U.S. President Donald Trump wants calm restored to Iraq as quickly as possible, and any airstrike on the country undermines its stability and deters foreign investors and donor states. Consequently, Iran is the one country whose trade with Iran has been exempted de facto from U.S. sanctions.

U.S. spy planes have recently intensified operations along the Iraq-Syria border. This may be a way of signaling to Israel that America will take care of preventing the smuggling of sophisticated arms to Hezbollah and Iranian-backed militias in Iraq and Syria. Alternatively, America may have started taking action against Iran’s entrenchment in Iraq for fear that Iranian-sponsored militias in Iraq will attack U.S. forces.

Shi’ite militias are the second cornerstone of Iran’s military entrenchment in Iraq, alongside its missile deployments. Economic problems and growing religious extremism in many Arab countries have enabled Iran to recruit volunteers for the militias it supports. And these militias let it carry out military operations without taking responsibility for them.

Iran had ties with militias in Iraq even back in the 1980s and 1990s. But these militias have become more powerful militarily as technology improved and as their political power grew.

Iran provides them with military, economic, logistical and religious support. In exchange, they will help Iran if it asks them – including, according to a senior Israeli defense official, by coming to the Lebanese or Syrian borders to participate in fighting against Israel. The Dado Center for Interdisciplinary Military Studies, which is part of the Israel Defense Forces, also said in recent reports that Israel must take these militias into account in future fighting.

The strongest Iranian-backed militia is Lebanon’s Hezbollah, the model Iran seeks to replicate in other countries. Since 2014, it has also supported a network of Shi’ite militias in Iraq. These militias, now known as the Popular Mobilization Units, are second only to Hezbollah in terms of their importance to Iran. They united under the Popular Mobilization Units umbrella at the urging of Ayatollah Ali Sistani, the Iranian-born cleric who is the spiritual leader of Iraqi Shi’ites.

The strongest militia in the PMU is the Badr Organization, which has both a political and a military wing. The latter is thought to have some 50,000 fighters. The Badr Organization is headed by Hadi al-Amiri, a former transportation minister who is close to Qassem Soleimani, the head of the Iranian Revolutionary Guards’ Quds Force. The organization also fought alongside America against the Islamic State.

Another important element of the PMU is Kata’ib Hezbollah. It was founded by Abu Mahdi al-Muhandis, an Iraqi Shi’ite trained in Iran to establish an Iraqi organization resembling the Quds Force. He is very close to Soleimani and has said in the past that he’s willing to fight alongside Iran.

The PMU also includes Asa’ib Ahl al-Haq, which has perpetrated attacks on American forces in Iraq. Its leaders are very close to senior Hezbollah officials, and Hezbollah helps fund it. Asa’ib Ahl al-Haq also gets millions of dollars each month from Iran.