Thousands of Marines Head to the Middle East as the U.S.-Iran War Enters Its Fourth Week With No Exit in Sight

The Pentagon announced on March 20 that a second Marine Expeditionary Unit—approximately 2,200 Marines aboard three warships—has departed California bound for the Middle East, the latest reinforcement in a conflict that has killed more than 2,000 people across the region, disrupted global energy markets, and triggered the largest U.S. military buildup in the Middle East since the 2003 invasion of Iraq [1][2].

The deployment of the 11th Marine Expeditionary Unit (MEU) aboard the USS Boxer, USS Comstock, and USS Portland—accompanied by roughly 2,000 sailors—comes as the Okinawa-based 31st MEU is already en route from Asia [3]. If both units receive final orders to the Middle East, it would add close to 9,000 additional forces to the approximately 50,000 U.S. troops already stationed in the region [4][5].

How the War Began

Operation Epic Fury, the U.S. codename for the campaign, launched on February 28, 2026, with a coordinated U.S.-Israeli strike against Iranian military and nuclear infrastructure [6]. Israel's parallel operation, Roaring Lion, struck simultaneously. The opening salvo killed Iran's Supreme Leader Ali Khamenei and other senior regime officials, triggering immediate Iranian retaliation with hundreds of ballistic missiles and thousands of drones targeting U.S. and allied positions across the region [7][8].

The strikes followed weeks of failed nuclear negotiations. Iran and the U.S. had begun indirect talks in Geneva in early February, mediated by Oman, aimed at curbing Tehran's nuclear program. When the third round of negotiations on February 28 produced what the administration called "unsatisfactory results," strikes commenced within hours [7].

The Trump administration has offered multiple justifications for the operation: protecting U.S. forces in the region, preempting an imminent Iranian threat, destroying Iran's ballistic missile and drone manufacturing capability, preventing Iran from obtaining a nuclear weapon, and securing freedom of navigation in the Strait of Hormuz [9][10]. Critics, including some within the administration's own former ranks, have noted these shifting rationales as a sign that the war's objectives remain poorly defined [11].

The Troop Buildup: Scale and Composition

Beginning in late January 2026, the Pentagon began positioning air, naval, and missile defense assets across the Middle East at a scale not seen in over two decades [4]. The current deployment wave represents a significant escalation of that buildup.

The 11th MEU aboard the USS Boxer Amphibious Ready Group departed California this week. The USS Tripoli, described as the most advanced "big deck" amphibious warship in the fleet—capable of carrying F-35 stealth fighters, Ospreys, and other aircraft—is also believed to be carrying Marine ground troops toward the region [3][12]. A separate Military.com report placed the latest deployment figure at approximately 2,500 additional Marines [5].

For context, each MEU represents roughly 1.2% of the Marine Corps' approximately 180,000 active-duty personnel. Deploying two MEUs simultaneously to a single theater is unusual and strains the Corps' global readiness posture.

At peak Iraq War levels in 2007, the U.S. had roughly 170,000 troops in Iraq alone. The current Middle East footprint of 50,000-plus, while substantially smaller, is the largest concentration since that era and is growing [4].

Source: Pentagon / Military.com / Wikipedia

Data as of Mar 21, 2026CSV

American Casualties

Thirteen American service members have been killed in Operation Epic Fury as of March 20, and the number of wounded has surpassed 200 across seven countries [13][14].

The deadliest single incident occurred on March 2, when an Iranian drone strike hit a makeshift operations center in Kuwait, killing six U.S. soldiers [15]. No warning or siren preceded the attack, according to CNN's reporting. An additional six airmen died on March 12 when their KC-135 aerial refueling tanker crashed in western Iraq during combat support operations [13]. Sgt. Benjamin N. Pennington, wounded in an attack in Saudi Arabia on March 1, died from his injuries on March 9 [13]. A National Guard soldier died from a health-related incident in Kuwait on March 6 [13].

The Pentagon has stated that the "vast majority" of the 200-plus wounded have sustained minor injuries, with more than 180 already returned to duty [16]. The Pentagon has not publicly articulated what it considers acceptable casualty levels for the operation.

The $200 Billion Question

The financial costs are mounting rapidly. The war cost an estimated $3.7 billion in its first 100 hours, according to the Center for Strategic and International Studies—roughly $900 million per day [17]. Munitions expenditure alone ran approximately $2 billion per day during the opening phase before dropping to roughly $1 billion daily [18].

By March 18, the Pentagon had submitted to the White House a request for Congress to approve a supplemental budget of more than $200 billion to fund continued operations [19][20]. At current spending rates, that funding could sustain the war for an estimated 100 to 200 additional days [21]. Defense Secretary Pete Hegseth, asked about the figure, responded: "Takes money to kill bad guys" [20].

Kevin Hassett, director of the White House National Economic Council, put total war costs at $12 billion as of mid-March [19]. The CSIS updated estimate was higher—$16.5 billion through the war's 12th day [17].

No supplemental spending bill has yet been introduced in Congress. The request would represent the largest single wartime appropriation since the early years of the Iraq and Afghanistan conflicts.

The Strait of Hormuz Crisis

Iran's most consequential retaliation has been at sea. Starting March 4, Iranian forces declared the Strait of Hormuz—through which roughly 20% of the world's daily oil supply transits—effectively closed [22].

As of March 12, Iran had carried out 21 confirmed attacks on merchant vessels [22]. Tanker traffic dropped by approximately 70% initially, with over 150 ships anchoring outside the strait. Traffic soon fell to near zero [22]. The Iranian Revolutionary Guard Corps has also attempted to mine the strait; U.S. forces have destroyed more than 30 mine-laying vessels, but Iran has adapted by using smaller boats [22].

The disruption has been described as the largest to global energy supply since the 1970s oil crisis [22]. Iran has also struck UAE energy infrastructure, setting a gas field ablaze and hitting a tanker near Fujairah [23].

Source: U.S. Energy Information Administration

Data as of Mar 16, 2026CSV

West Texas Intermediate crude oil prices surged from $66.96 per barrel on February 27—the last trading day before the war—to $98.48 on March 13, a 47% increase in two weeks [24]. Brent crude, the international benchmark, reportedly peaked at $126 per barrel [22]. Prices have since pulled back slightly to $93.39 as of March 16 [24], but remain far above pre-war levels, with fuel shortages and rationing already reported in parts of Asia [22].

The Legal and Constitutional Dispute

The war rests on contested legal ground. President Trump's war powers notification to Congress, submitted March 2, cited his "constitutional authority as Commander in Chief and Chief Executive to conduct United States foreign relations" under Article II [25][26]. The administration has not invoked the 2001 Authorization for Use of Military Force—which targeted al-Qaeda and associated forces—or any other statutory authorization.

This matters because Congress repealed the 2002 Iraq AUMF in 2023, and the 2001 AUMF has never been interpreted to cover Iran. No Iran-specific authorization for the use of military force exists [25].

Legal scholars are sharply divided. Yale Law Professor Oona Hathaway called the strikes "blatantly illegal" under both U.S. and international law, noting that the Constitution grants Congress—not the president—the power to declare war [25]. NYU's Peter Shane acknowledged "genuine disagreement" in constitutional interpretation, noting the Justice Department has historically defended unilateral presidential force when it serves "sufficiently important national interests" without "prolonged and substantial military engagement" [25]. Three weeks into the conflict, whether the engagement qualifies as "prolonged and substantial" is increasingly difficult to dispute.

Congress has attempted—and failed—to assert its war powers authority. On March 4, the Senate rejected a Democratic-led war powers resolution 47-53, with Sen. Rand Paul (R-KY) as the sole Republican voting in favor and Sen. John Fetterman (D-PA) the only Democrat opposing [27][28]. The following day, a parallel House resolution failed 212-219, largely along party lines [29].

Sen. Tim Kaine (D-VA), a longtime advocate of war powers reform, and Rep. Thomas Massie (R-KY) led bipartisan efforts in their respective chambers. Sen. Elissa Slotkin (D-MI), a former CIA analyst and Pentagon official, called the conflict "a war of choice" that demands congressional authorization [30].

A January 2026 Quinnipiac poll—taken before the strikes—found 70% of voters opposed military action against Iran [27].

What Happens Without These Forces

The Pentagon's case for the deployment centers on several assessed risks if the U.S. were to withdraw or refrain from reinforcing.

Freedom of navigation through the Strait of Hormuz is the most immediate concern. With Iran actively mining the strait and attacking commercial shipping, the U.S. Navy's ability to escort vessels and conduct mine-clearing operations depends on sufficient naval presence [22][31]. CENTCOM Commander Admiral Brad Cooper has stated that "eliminating the threat Iran poses to ship movement through the Strait of Hormuz" is a core U.S. military objective [9].

Regional allies—Saudi Arabia, the UAE, and Israel—face direct Iranian missile and drone threats. Hezbollah launched missiles and drones into Israel on March 2, prompting an escalation in Israeli air strikes extending to southern Beirut [7]. Iran's attacks on UAE energy infrastructure demonstrate a willingness to target Gulf state economic assets [23].

The intelligence community's assessment of Iran's willingness to escalate if it perceives U.S. weakness has not been made public. However, Iran's pattern of retaliation—attacking Hormuz shipping, striking at Kuwait and Saudi bases, and activating Hezbollah—suggests a strategy of imposing maximum cost across the broadest possible front [7][22].

No Timeline, No Exit Criteria

The administration has articulated no public timeline for the deployment or criteria for drawdown. When asked about ground troops on March 20, President Trump stated: "No, I'm not putting troops anywhere. If I were, I certainly wouldn't tell you. But I'm not putting troops" [2]. A White House official separately told reporters: "There has been no decision to send ground troops at this time, but President Trump wisely keeps all options at his disposal" [1].

This framing—deploying thousands of Marines aboard amphibious warships while denying ground troop deployment—reflects a semantic distinction between forces aboard ships and forces on foreign soil. But MEUs are, by design, expeditionary ground forces intended for rapid deployment ashore.

The stated military objectives of Operation Epic Fury—destroying Iran's ballistic missile capability, eliminating its naval threats, dismantling proxy networks, and preventing nuclear weapons development—are expansive [9][10]. None comes with a declared metric of success or a conditions-based withdrawal framework.

The war has already displaced hundreds of thousands in Lebanon, stranded hundreds of thousands of travelers across the Middle East, and killed more than 2,000 people in Iran, Lebanon, and Israel combined [7]. With two Marine Expeditionary Units now steaming toward the conflict zone and a $200 billion supplemental spending request on the table, the U.S. commitment is deepening—without a declared endpoint, congressional authorization, or public criteria for what victory looks like.