Iran’s recent seizure of the merchant ships Stena Impero and Mesdar on 19 July was retaliation for the previous British seizure of the Iranian-owned merchant ship Grace at Gibraltar on 4 July. The British claimed Grace was violating sanctions on shipments of fuel to Syria. Iran justified seizing Stena Impero and Mesdar as an equivalent response. While this possibly is true of the Mesdar, seizing the Stena Impero in fact represents a serious escalation.
The Grace is Panamanian-flagged and the Mesdar, briefly held and then released, is Liberian-flagged. Thus, the Iranian capture of the Mesdar can be seen as an equivalent response to the British capture of the Grace—that is, each of these two ships was sailing under a flag of convenience, rather than under the flag of the country of the ship’s owner. Under international maritime law and practice, the British did not “attack” the flag of Iran with the seizure of the Grace, and the Iranians did not “attack” the flag of Britain with the taking of the Mesdar.
However, the Stena Impero is British-owned and British-flagged. An attack on that ship can be viewed under international law and practice as equivalent to an Iranian attack on British territory. Many times in the past such an incident has been regarded as a potential casus belli—a cause for war.
The practice of “flags of convenience” issued by small states began with Panama in the 1920s followed by Liberia in 1948, and expanded to more than 20 nations by the end of the 20th century. Shipping companies benefited from less expensive registration and usually no requirement to employ crews from the nation of ownership. In some cases, in addition to these economic advantages, there sometimes were less stringent safety requirements, although in the case of large tankers, the ships and cargoes are so valuable that ship owners insist on qualified crews and strict adherence to safety practices.
Before flags of convenience, the United States went to the brink of war over many incidents in which a foreign navy attacked, detained, or otherwise interfered with the free passage of a U.S.-flagged ship in international waters. Among the many cases in the late 19th century were several that contributed to the growing demand for an expanded and effective U.S. Navy to protect the U.S. merchant flag. For example:
- Two cases of Canadian interdiction of U.S fishing vessels in 1886—the Adams and the Marion Grimes
- Two 1887 cases of Nicaragua forcibly searching U.S.-flagged ships Merida and William S. Moore in international waters
- One 1888 case of a Portuguese ship interfering with the U.S.-flagged ship Mary Frazier
- A major episode when the Spanish gunboat Conde de Venaditio fired on the U.S.-flagged Allianca off Cuba in March 1895
These episodes (and six minor engagements) from 1886 to 1895 all contributed to newspaper and public outcry for a more modern steel-and-steam U.S. Navy to protect the U.S. maritime flag. Of course, that “new Navy” did play a crucial role in the brief Spanish-American War, provoked by the loss of the USS Maine in Havana Harbor on 15 February 1898.
It was the German sinking of three U.S.- flagged merchant ships in March 1917—the Vigilancia, the City of Memphis, and the Illinois—that provided the immediate cause for the United States to declare war. Although the more spectacular sinking of the British liner Lusitania on 7 May 1915, that included the loss of 128 American lives, is better-remembered, it was the sinking of these three small U.S.-flagged merchant ships (with very few casualties) that finally convinced President Woodrow Wilson to ask the Congress for a declaration of war on Germany in April 1917. This point is crucial—it was the attack on the U.S. merchant ship flag, not the loss of American life, that led the United States into World War I.
From 1939 to 1941, U.S. owners of tankers and cargo ships regularly transferred ship registrations to the Panamanian flag to carry valuable cargoes to Great Britain. These transfers were effected precisely so the U.S. could supply Britain (and France to an extent) with petroleum and other products without violating official U.S. neutrality. When some of those ships were sunk by German U-boats, depite the loss of U.S. cargo and ships, the United States could remain neutral precisely because the U.S. flag had not been attacked on the high seas by the German Navy. None of the crew members on board these flag of convenience ships were U.S. citizens.
Given this history, the Iranian attack on a British-flagged ship, rather than on a ship flagged in one of the several flag of convenience states such as Panama or Liberia, could be regarded as an Iranian act of war against the United Kingdom. The Royal Navy is much diminished over the past few years, a fact that limits Britain’s ability to respond forcefully to an attack on its flag. Diplomacy may resolve this particular issue, but Iran took a step closer to war against a maritime nation for the first time since the 1980s. A similar seizure of a U.S.-flagged tanker could prompt a military response in the tradition of defending the U.S. flag at sea.