Three small Persian Gulf Islands emerging as an issue and possible war prize in the conflict between Iran and Iraq are the site of a past Iranian triumph in the days of the late shah's regional ascendancy and an Arab humilitation that Iraq has been eager to avenge.

The three -- Greater Tumb, Lesser Tumb and Abu Musa -- have no particular economic value. But their position at the entrance to the Strait of Hormuz gives them command over oil tankers passing in and out of the Persian Gulf and confers on them a strategic importance that has grown with the price of petroleum and the West's dependence on the Gulf for continued supplies.

Iranian Navy and Army forces occupied the islands in a swift operation in November 1971, meeting only slight resistance from local police forces on Greater Tub. The late shah cited the need to protect Gulf shipping, a mission he shouldered at the time with U.S. encouragement.

But for many Arabs, his move stood for a land grab in the perennial competition between Arabs and Persians for supremacy in the vital waterway.

The islands previously had been controlled by Britain. As the British pulled out of the area, the sheikdom of Ras al-Khaimah renewed a claim to Greater Tumb and the uninhabited Lesser Tumb and the sheikdom of Sharjah claimed the 2 1/2-mile stretch of Abu Musa. Both sheikdoms are part of the United Arab Emirates, a federation that succeeded Britain's Trucial States.

Iran ignored the claims, however, and has stationed military forces on the islands since the takeover. Despite the shah's departure, the revolutionary government of Ayatollah Ruhollah Khomeini has upheld Iran's claim to sovereignty there and maintained Iranian forces to back it up.

Iraq has renounced any aspiration to control the islands itself. But, in a manifestation of Baghdad's growing ambition to the role of regional power, it has insisted that the islands return to Arab rule and made that demand part of its list of grievances against Tehran.