Tensions are simmering. Internal strife, aggression, and military buildup.

Iran’s long-simmering proxy war with the U.S. and Israel is quickly heating up, and it’s forcing the Pentagon to shift more naval and air assets to the Middle East as a deterrent.

Tehran-backed militias have launched a string of attacks on American bases in northern Syria since late March, killing one U.S. contractor and leaving at least six others with traumatic brain injuries. The Palestinian militant group Hamas and other Iranian proxies fired missiles into Israel this month in a coordinated strike from three separate borders — Lebanon, Syria, and the Gaza Strip.

U.S. and Middle Eastern officials who spoke with Semafor, as well as outside analysts, said they believed the stepped-up assaults were part of a new effort to test the willingness of American and Israeli forces to respond to acts of aggression.

Tehran’s growing military assertiveness, they said, was likely connected to its recent deal to normalize relations with Saudi Arabia and other Arab states, which has given it more room to focus on American and Israeli targets away from the Persian Gulf. Fighting between Iranian-backed Houthi rebels and Saudi forces in Yemen, for instance, has largely come to an end, and the two sides are close to signing a formal peace agreement soon.

“The Iranians calculate the advantage is theirs on regional issues,” said Emile Hokayem of the International Institute for Strategic Studies in London. “They think they have split the Saudis and Emiratis from the U.S. and Israel. Iran can now work to widen that gap.”

Iran has vowed to retaliate against Israel for its attacks on its military personnel and infrastructure inside Syria. Earlier this month, an Israeli airstrike killed a senior Islamic Revolutionary Guard Corps official outside Damascus. The IRGC said in a statement that the “Zionist answer regime will receive the for this crime."

However, recent internal strife within Israel over Prime Minister Benjamin Netanyahu’s controversial court plan may also be a factor, sources told Semafor. As one Arab official put it, the Iranians “strike when they sense vulnerability.” Tehran has also urged its allies to confront Israeli forces who have clashed with Muslim worshippers at Jerusalem’s Al-Aqsa Mosque this month.

The Pentagon announced in recent days that it’s moving the George H. W. Bush carrier group to the Mediterranean to better protect U.S. troops in Syria. The Navy has also dispatched a guided-missile submarine, the USS Florida, to the region to guard against Iranian attacks on American and Israeli shipping.

Tehran says it’s closely monitoring these deployments. "Washington had better come to grips with the new realities [on the ground] and refrain from any effort to intervene in the West Asia region and the Persian Gulf,” said Iran’s foreign ministry spokesman on Monday.