U.S. sinking Iranian warship threatens security of Indian Ocean nations

On March 4, a U.S. submarine some 40 nautical miles south of Sri Lanka in the Indian Ocean sank the Iranian navy frigate IRIS Dena with a MK-48 torpedo, resulting in 87 deaths and dozens missing.

Periscope footage of the sinking. Photo/AFP

This attack not only represents a tactical escalation in the U.S.-Iran conflict but also poses a serious threat to national security and geopolitical stability in the Indian Ocean region. The action broke the tacit of "non-spillover of the Gulf conflict," bringing warfare to a global shipping choke point.

The Indian Ocean serves as a "maritime lifeline" connecting the Middle East, Africa, South Asia, and East Asia. The spread of conflict could lead to a surge in international shipping insurance rates and potentially cause vessels to reroute, impacting global energy and trade supply chains.

The attack occurred within Sri Lanka's Exclusive Economic Zone (EEZ), forcing non-belligerent nations like Sri Lanka into involvement in search, rescue, and aftermath operations. This disrupts the peaceful status of its sovereign waters and increases the security burden on regional states.

 

Iranian warship IRIS Dena in the Bay of Bengal during International Fleet Review in on February 18. Photo/AP

The U.S. military has set a dangerous precedent of launching strikes on the high seas "without warning and against a vessel not exercising self-defense." This not only tramples on the United Nations Convention on the Law of the Sea (UNCLOS) but also sends a perilous signal that "major powers can freely use force on the high seas," posing a direct threat to the maritime security of smaller and medium-sized nations.

The targeted vessel was returning from participating in the "MILAN-2026" multilateral naval exercise hosted by India when it was attacked. India, as the host of MILAN-2026, did not provide escort, warning, or rescue in this incident, exposing the fragility of its security commitments in what it considers its "backyard" — the Indian Ocean.

This U.S. action is not only a military strike against Iran but also a political and diplomatic affront to Iran's partners, attempting to sever Iran's blue-water diplomatic reach. This places immense pressure on the diplomatic balancing acts of South Asian nations such as India and Sri Lanka.