The maritime interception operation conducted by Task Group 627.4, under Commodore Don Chalmers, in the Gulf of Oman from 3 September to 3 December 1990 was a new and demanding challenge for the Royal Australian Navy (RAN). Indeed, when the Australian ships first sailed from Sydney they did not even know much about the nature of their mission. It was not certain whether they would be part of a UN force or a US-led force, and command arrangements had yet to be determined. The new challenge, however, related not just to the command arrangements but also particularly to learning and developing the techniques for conducting interception operations. And in this respect the first question was to decide whether they would be involved in a blockade, sanctions, quarantine, interdiction, interception or embargo operation.
According to the RAN's doctrine, a blockade is ‘an operation intended to disrupt the enemy's economy by preventing ships of all nations from entering or leaving specified coastal areas under the occupation and control of the enemy. Blockade is an act of war and the right to establish it is granted to belligerents under the traditional laws of war.’ In other words, a blockade is a strategy employed in a war. Economic sanctions, however, are generally applied by the international community against recalcitrant nations in an effort to persuade them to modify their behaviour. For example the League of Nations tried, ineffectually, to apply sanctions against Italy after it invaded Ethiopia in 1935.