Changes in the balance of power in the Arabian Peninsula and adjacent Indian Ocean areas may follow the unexpected shift in leadership in South Yemen. The resignation of President Abdul-Fattah Ismail on April 21 in what apparently was an internal political struggle naturally has stirred speculation over whether his successor will continue the country's strong Marxist orientation.
Mr. Ismail has been succeeded as head of state and of the ruling Yemeni Socialist Party (YSP) by his long-time political ally, Ali Nasser Muhammad.
The official news agency said that the central committee of the YSP also had removed Mr. Ismail from his position as secretary-general of the party, assigning him instead to the newly created post of president of the party.
This new job is thought to be largely honorary.
The Marxist People's Democratic Republic of Yemen, as South Yemen is known officially, occupies a unique position on the Arabian Peninsula by virtue of its 12-year cooperation with the Soviet Union. This culminated in Mr. Ismail signing a treaty of friendship and cooperation between the two countries in Moscow last November.
South Yemen officials deny that there are any Soviet military bases in their country. But Soviet warships are believed to enjoy fueling and other facilities at Aden, a key British naval base before Britain withdrew from Aden in 1967.
Among a number of other economic links, the Soviets have brought business to Aden's large state-owned oil refinery, helping to get it back on its feet after the closure of the Suez Canal in 1967 cut its highly profitable business to a minimum.
Mr. Ismail had been an active proponent of close links with the Soviet bloc. he made a number of visits to Moscow after his first visit in 1970 as secretary-general of the Yemeni Socialist Party's forerunner, the National Liberation Front.
It is too soo to know if Mr. Ismail's surprise ouster means that South Yemen can be drawn away from the Soviet sphere of influence. His successor, Mr. Muhammad, was associated with him in most of his pro-Soviet moves throughout the 1970s, as well as in the overthrow of former President Salim Ali.
Mr. Muhammad has favored the development of relations with other states of the peninsula whose oil wealth could be used to develop South Yemen's scanty infrastructure, but he is generally regarded as refusing to have any political strings attached to aid projects.
Arab specialists on Yemeni affairs say the rift now apparent between Mr. Ismail and Mr. Muhammad is part of a struggle for power between the two men which has continued in the YSP's inner sanctum for some months now. They say Mr. Ismail's supporters have gradually been losing ground.
The Saudis, who have nearly a million Yemeni workers running many of their basic services, already are worried about the recent growth of Soviet influence in neighboring North Yemen. They doubtless hope that an opposite trend can redress the balance in South Yemen.