SOUTH AFRICA'S POLITICAL structure resembles a pyramid. At the base are the 22 million blacks (Africans, coloreds of mixed descent and Asians). Above them are the ruling 4-1/2 million whites. But the whites are stratified again into an Afrikaner elite -- about 3 million of them -- and a motley English-speaking community composed of the remaining 1-1/2 million, no more than hangers-on in the political process: a ruling class superimposed on a ruling class. And at the core of the Afrikaner section is the Broederbond (bond of brothers), probably the most powerful secret society in the world.

At a time when secret societies are falling out of fashion, except perhaps in gangland or in the mysterious East, the Broederbond manages to be uniquely influential, counting prime ministers among its members and Afrikaner domination of South Africa as its declared achievement.

The Broederbond winds its grip around South Africa like an octopus. Its 12,000 carefully chosen members, grouped in about 800 cells, hold key positions in almost every walk of life. The prime minister, Pieter Botha, is a brother, as all prime ministers have been since the Afrikaner election victory in 1948. So are all members of Botha's cabinet, with two significant exceptions: the minister of finance, Senator Owen Horwood, who is disqualified by being English-speaking, and Marais Steyn, minister of community development, colored relations and Indian affairs, a defector from the opposition.

The Broederbond was founded in 1918 when the Afrikaners, following their defeat in the Boer War (1899-1902), were struggling to find their feet. Initially, the Broederbond's enemy was British hegemony over South Africa: political, economic, cultural. The Afrikaners saw themselves as the downtrodden poor whites. Later, after English-speaking hegemony had been replaced by Afrikaner hegemony, except in the business field, the Broederbond turned its attention to consolidating white rule over the black population.

Only the purest of the pure can join the Broederbond, and then by invitation only. They must be male protestant Afrikaners -- women are excluded and must not expect to share their husband's Broederbond secrets. There are five cutoff points at which recruitment of a new member can be abandoned. Initiation takes place in a solemn religious atmosphere, performed by candlelight or under the dim glow of electric bulbs. Passages are read from the Bible, hymns are sung, and questions are put to the initiate, who vows to keep Broederbond secrets until his death.

The secret Broederbond handshake has been discarded because it became too well-known, but other secret signs are still used. The organization's symbol is a triangle inside a circle with the words Afrikaner Broederbond on top, and 1918, the founding year, at the bottom. The organization has its own song, and its headquarters is masked behind the facade of an Afrikaans cultural federation. When Broederbonders hold their secret meetings, they scatter their cars around the area to divert attention, they do not dine afterwards in public places, and if they hold barbecues on private property they do not engage black servants to cut the meat and keep the fires burning.

In another context, these practices would be childish games. Instead, they constitute a well-structured, effective method of recruiting an Afrikaner elite, protecting its secrecy, and building a lifelong cohesion and commitment to Afrikaner power and white survival. When a whole ruling class, from the prime minister down, plays these games, they are no longer games.

The Broederbond has yielded up its secrets on only five occasions in the past 61 years. The first was in 1935 when an Afrikaner prime minister, General Barry Hertzog, in a major expose, denounced both the Broederbond and his son, Albert, for belonging to it. Hertzog asked: "When will that foolish, fatal idea cease with some people that they are the chosen of the gods to govern over all others?"

On the second occasion, during World War II, military intelligence in South Africa bugged a Broederbond conference. The third disclosure came in 1963 from an Afrikaner clergyman, the Rev. Beyers Naude, who quit a senior Broederbond position to become director of the multiracial, ecumenical Christian Institute of Southern Africa, now banned. The fourth disclosure, if it can be called a disclosure, followed the exposure in the Johannesburg Sunday Times of the secret documents released by the Rev. Naude: The government appointed a commission to inquire not only into the Broederbond, but also into the Freemasons, and gave each a clean bill of health.

Finally, in 1977, the Naude disclosure repeated itself: A long-standing Broederbond member telephoned the Sunday Times and offered the newspaper more secret documents. But it took him a year to pluck up the courage actually to call at the newspaper's office, explain his mission to Ivor Wilkins and Hans Strydom (reporter and news editor, respectively), and lead them to a stash of Broederbond documents in a house in the suburbs.

J. H. P. Serfontein's Brotherhood of Power is based on the 1963 disclosures, and Wilkins and Strydom's The Broederbond, is based on the 1977 disclosures. The books overlap to some extent, but in other ways they complement each other. Together, they provide a penetrating insight into the Broederbond and its machinations; so much so, that the bond has felt obliged to respond with its own "official" history.

A significant pointer to the Broederbond's influence has been the appointment by prime minister Botha of Dr. Gerrit Viljoen, the present chairman of the Broederbond and rector of the Rand Afrikaans University, as administrator-general of Namibia. Dr. Viljoen's task is to minimize the rift in the Afrikaner community in Namibia over the liberalization of apartheid laws -- an example of the Broederbond's classic unifying role.

South Africans are included to disagree about the extent of Broederbond power. Some say the organization cannot dictate to the cabinet. But the bond is not a separate power grouping: It is interwoven with the political process and, indeed, often acts as a think tank for it. It monitors the government's progress and registers the minutest flickering of the needle on the Afrikaner seismograph.

Wilkins and Strydom put it this way: "The South African government today is the Broederbond and the Broederbond is the government. No Afrikaner government can rule South Africa without the support of the Broederbond. No nationalist Afrikaner can become prime minister unless he comes from the organization's select ranks." Perhaps it is true that the Broederbond does not govern South Africa; but that it is Broederbonders who govern South Africa is beyond doubt.