Prince Sultan bin Abdulaziz Al Saud, heir presumptive to the throne of Saudi Arabia, died in hospital in New York City on Saturday. Sultan, in his eighties, had been battling cancer for years.

Half brother to Saudi king Abdullah, Sultan was defense minister for nearly fifty years before the monarch appointed him deputy prime minister in 2005, a post traditionally held by the next in line to the throne.

The likeliest candidate to replace Sultan as Abdullah’s successor is Prince Nayef, the conservative interior minister who is in charge of Saudi Arabia’s internal security service.

All brothers are sons of Ibn Saud, the founder of the modern Saudi kingdom who died in 1953. The order of succession to the throne usually follows agnatic seniority but a prince may be surpassed if there is a consensus in the royal family.

King Abdullah attempted to formalize the succession process in 2006 when he created the Allegiance Council to name the future monarch. The council is composed of three dozen sons and grandsons of Ibn Saud’s.

Whoever succeeds Abdullah, who has also underwent medical treatment in the United States repeatedly in recent years, is unlikely to upset the kingdom’s close relationship with Washington but may stir some internal discord. Abdullah is regarded as a cautious reformer who has improved the position of woman in the country. Nayef, for all his efforts combatting Islamic radicalism in the wake of two terrorist attacks that struck the kingdom in 2003, is more closely allied to the ultraconservative Wahhabi clergy which provides the Al Saud the religious legitimacy they need to govern.

More immediately, Sultan’s death will have repercussions for the Saudi defense establishment. The uncontested master of the oil kingdom’s military since 1962, Sultan fostered personal relations with American defense contractors and military officials. Although he was involved in numerous corruption scandals, Sultan’s influence never eroded before his health began to deteriorate in the previous decade.

One of Sultan’s sons, Prince Khaled, longtime deputy defense minister and commander of Saudi Arabia’s forces during the First Gulf War, is expected to succeed him.