Legal Implications of the US Navy's Attack on Iranian Warship IRIS Dena

Introduction to the Incident

The recent sinking of the Iranian warship IRIS Dena by the US Navy in the Indian Ocean has sparked a significant legal debate: does this incident represent a legitimate act of war or a violation of international law? This event follows a series of escalating tensions in the Middle East, particularly after the US launched Operation Epic Fury, which has further complicated the regional conflict.

Understanding the Legal Framework

The resolution to this legal question hinges on the international laws that govern military engagement and the conduct of warfare. These laws are categorized into two main areas:

• Jus ad bellum – which dictates the conditions under which states may resort to force.
• Jus in bello (Law of Armed Conflict / International Humanitarian Law) – which regulates the conduct of hostilities once they commence.

According to Captain SB Tyagi (Retd), an Indian Army veteran and academic, determining whether the sinking of the IRIS Dena constitutes a war crime depends on the application of these two legal frameworks to the incident.

Was the Use of Force Justified?

The IRIS Dena had recently docked in Vishakhapatnam, India, for Exercise MILAN, which took place from February 18 to 25. Although the US Navy was invited to join the exercise, they withdrew at the last moment. The Iranian warship was returning home when it was hit by a Mark 48 torpedo from a US submarine in the Indian Ocean. Sri Lankan military personnel responded promptly to a distress call from the frigate.

It is important to note that the IRIS Dena was operating under reduced armament protocols as mandated by Exercise MILAN. According to Article 2(4) of the UN Charter, the use of force against another state's territorial integrity or political independence is prohibited, with two notable exceptions:

• Self-defense as outlined in Article 51
• Authorization from the Security Council

Greenwood points out that self-defense is often cited as the primary justification for military action. The US could argue that the attack was lawful if:

• IRIS Dena posed an immediate threat to US forces
• It was involved in supporting Iranian assaults on Israel or US interests
• The response was necessary and proportionate

Was There an Armed Conflict?

International humanitarian law comes into play once an armed conflict is established. Greenwood notes that the definition of armed conflict is quite expansive: any engagement between the armed forces of two nations qualifies, regardless of its duration or scale.

Thus, if US forces engaged an Iranian naval vessel, it would legally escalate to an international armed conflict. Captain Tyagi emphasizes that once this threshold is crossed, the comprehensive laws of war become applicable.

Military Objectives and Legal Attacks

Under the law of armed conflict, military objectives can be legitimately targeted. Greenwood explains that combatants must differentiate between military and civilian targets, attacking only those that are legitimate military objectives. A naval combat vessel is clearly a valid military target, meaning that sinking a warship is not inherently illegal. Historical precedents include:

• Falklands War: The sinking of the Argentine cruiser ARA General Belgrano by HMS Conqueror
• Iran-Iraq War: Naval engagements during the Tanker War
• Operation Praying Mantis (1988): The US's destruction of Iranian naval units

Military Necessity and Proportionality

Even legitimate targets must satisfy the criteria of military necessity. The law stipulates that the use of force must be essential to repel or halt an attack. For instance, during the Falklands War, the sinking of the Argentine cruiser General Belgrano was contentious because critics argued it was not necessary for reclaiming the islands.

Greenwood uses this case to illustrate how necessity influences legality in naval warfare. If the IRIS Dena was merely sailing away, not engaged in hostilities, or outside the conflict zone, the legality of the attack becomes questionable.

The Principle of Proportionality

Another critical legal principle in engaging the enemy is proportionality. The law mandates that attacks must avoid excessive civilian casualties in relation to the anticipated military advantage. This principle is particularly relevant in air strikes, missile attacks, and urban combat. At sea, civilian casualties are generally limited unless civilian vessels are in proximity, the ship is navigating through commercial shipping lanes, or collateral damage occurs. Therefore, proportionality would only be a concern if civilian vessels were impacted, environmental damage was significant, or rescue operations were obstructed.

Distinction in Warfare

A fundamental legal rule is the principle of distinction. Commanders are required to differentiate between combatants and civilians. Warships like the IRIS Dena clearly fall into the combatant category, making the act of targeting the ship itself lawful. However, violations could occur if survivors were attacked, surrenders were ignored, or rescue efforts were deliberately obstructed, which would contravene the Geneva Conventions.

Context of Naval Warfare

Historically, naval warfare has fewer legal restrictions compared to land warfare, yet modern laws still impose limitations. Greenwood notes that advancements in technology—such as precision weaponry and long-range strikes—do not replace legal principles; rather, they are evaluated using the same standards of distinction and proportionality. Even cyber warfare or electronic attacks are assessed under these legal frameworks. Consequently, a missile strike on the IRIS Dena would be scrutinized under the same criteria as any contemporary naval strike.

When Would It Be Considered a War Crime?

The sinking of the IRIS Dena would only be classified as a war crime if it involved specific breaches such as:

1. Attacking a vessel that had surrendered: Under wartime law, ships that surrender must not be attacked.
2. Targeting survivors in the water: This would violate the Geneva Conventions.
3. Attacking a hospital ship or civilian vessel: Protected ships cannot be targeted.
4. Disproportionate collateral damage: If civilian ships or ports were affected.
5. Perfidy or deception: For instance, using false flags to lure the ship into surrender.

However, none of these violations are inherent in the act of sinking a warship itself. Greenwood emphasizes that states rarely disregard legal arguments entirely. Governments often seek legal justification for controversial operations to maintain international legitimacy. For example, the US legally justified its invasion of Panama in 1989 and NATO framed the Kosovo intervention in 1999 as humanitarian. Legal reasoning is frequently employed to uphold political legitimacy and coalition support. Nevertheless, beyond legality, the sinking of an Iranian warship could lead to significant strategic repercussions:

• Escalation into open US-Iran naval conflict
• Threats to close the Strait of Hormuz
• Iranian retaliation through proxies
• Wider regional conflict involving Israel

Legally permissible actions can still have profound geopolitical implications.