IN THE EARLY paragraphs of this excellent, even fascinating, but not flawless biography, Philip Ziegler tells of the favorite leisure-time occupation of Lord Louis Mountbatten, Earl Mountbatten of Burma. It was tracing out his genealogy, no slight task, involving family connections extending through an intricate German maze back to Charlemagne or perhaps beyond and, in more recent times, establishing him as a great-grandson of Queen Victoria, a nephew of a czar and czarina of Russia and, of course, the uncle of the husband of the Queen of England. He greatly preferred his genealogical research to reading or other more tedious pursuits. It also reflected sound judgment; no one was ever better served by the accident of birth or put royal connection to greater use.

Family background led to his choice of a naval career. Here he followed his father, Prince Louis of Battenberg, who at the beginning of World War I was the "First Sea Lord," effectively the uniformed head, of the British Royal Navy but who in the violent chauvinism of the day was presently expelled from office for having such an unwholesome German name. (This last misfortune, in the course of time, was repaired by his becoming Lord Milford Haven and the family not Battenberg but Mountbatten. The British do these things well -- or used to.)

Louis Mountbatten's early navy service was less than routine -- it involved such tasks as accompanying the Prince of Wales, later and with rewarding brevity Edward VIII, on journeys of state to Australia and India. However, he became fully involved with ships at the outbreak of World War II, when, as a destroyer commander, he began to compile one of the war's most remarkable records of disaster. This stemmed from his tendency to proceed at high speeds without evident prior thought as to what, in the way of other ships, mines or enemies, he might encounter. During the tense days of 1940, when England awaited the threatened invasion, he was almost always in dock while his ship was being fixed up following various largely preventable mishaps.

In ensuing months, Mountbatten was promoted to the command of a destroyer division and promptly lost his ship at Crete, though here perhaps through no grave personal fault. This led, inevitably, to a promise of further promotion to the command of an aircraft carrier, from which, mercifully for the crew, he was diverted to head Combined Operations. Here he planned and directed the raid on Dieppe, widely believed the single most ill-advised, costly and generally disastrous operation of the war. Accordingly, or at least predictably, in the months following, he was promoted to the post of Supreme Commander, Southeast Asia Command (SEAC), with headquarters first in New Delhi and then in Kandy in Ceylon (as it then was).

From Asia, Mountbatten lobbied London for permission to conduct amphibious operations against Burma, Malaya and Indonesia, as well as on behalf of his land operations in eastern India and Burma. With the amphibious operations he was not successful until after the Japanese surrender, when there was a landing on some Malayan beaches. Intelligence being poor, it was not known that the beaches were exceedingly soft, and so the transport and armored equipment got hopelessly bogged down. However, hostilities having ended, Mountbatten did not immediately get another navy promotion. The intelligence failure, it should be noted, could not be blamed on a shortage of personnel at his headquarters; by the end of the war Mountbatten had a staff at Kandy of around 10,000, which, it being a time of grave manpower shortage, even the tolerant authorities back in London thought rather large. Mr. Ziegler, who had access to the Mountbatten papers, cannot conceal his feeling that in the navy Mountbatten was an outstanding example of upward failure.

THERE IS little doubt that, throughout, Lord Louis was saved and helped by his royal connections -- his attention to genealogy continued to show a sound sense of what was important. But he also had three other qualities: He had great personal charm, as all who knew him can attest, unflagging self- confidence and an overwhelming desire to get things done. This last, in a military establishment in which caution and respect for tradition verged on inertia, attracted attention, not the least from Winston Churchill. All his life Mountbatten was repeatedly sought out by people who wanted less thought and more action, both of which he could provide.

At the end of the war yet another personal quality became evident. That -- with guidance and encouragement from Edwina, his diversely concerned, rich, talented and unquestionably very difficult wife -- was his ability to see that the age of imperialism was over. He made this apparent in both word and action, extending to association with those seeking independence in Burma, Indonesia and India and not rejecting, as most were inclined to do, those in Burma and Indonesia who had aligned themselves in the war with the Japanese and against their old imperial masters. Most of all, he showed his friendship and sympathy for Gandhi and Nehru, becoming, as even more did Edwina, a devoted friend of Nehru's. This led to the next and by a wide margin the greatest of his assignments -- to preside as viceroy over the partition of India and the proclamation of Indian and Pakistani independence and to serve thereafter as governor-general of the new Indian state. Then, still a relatively young man, he went back to a navy command, rose to be first sea lord, the post from which his father was sacked, and eventually head of all the more or less unified armed services. As first sea lord he strongly resisted the Suez misadventure of Anthony Eden, coming close to taking the unprecedented step of submitting his resignation. In these years he also became deeply aware of the way nuclear arms were robbing war of its old relevance and enjoyments. He was now clearly a force for the good -- judgment was for him increasingly an attribute of age.

Leaving office in 1965, Mountbatten passed into a notably reluctant and peripatetic retirement. He was killed in 1979 at the age of 79 by IRA terrorists while sailing near his Irish estate.

Mr. Ziegler has told this quite remarkable story in lucid detail, sometimes -- as in the case of the struggles over authority, command, weaponry and especially over rank and personal privilege in the Royal Navy, the British defense establishment and in the royal family -- in greatly excessive detail, at least for an American reader. He has also spent too much time deciding whether on this action or decision or that Mountbatten was right or wrong. (Especially when Mountbatten was wrong, Ziegler is tedious in his effort to find, however improbably, some trace of redeeming wisdom.) I've never been persuaded that facts speak for themselves; in my observation they can be very reticent as to the real truth. But it is not necessary to pass judgment, as Mr. Ziegler does, on everything.

On Mountbatten's most portentous decision, that taken as viceroy in March 1947 to abandon caution and press forward to Indian and Pakistani independence by mid-August, Mr. Ziegler could not, of course, avoid judgment. That and whether the vicious slaughter in the newly divided Punjab could have been avoided have been endlessly debated and are still a contentious subject. With others, I've wondered if a more gradual approach, with more appeals for calm and reason, more time for adjustment, might have served better. But Mountbatten, as ever, was impatient for the action. The larger truth is that no one knows. By the time the Mountbattens arrived in India, there had ceased to be any alternative to partition. Positions, especially that of Jinnah, were fixed, irrevocable. Perhaps delay would only have meant months of mounting anger and more deaths when partition and independence finally came.

To return to Mountbatten's career as a whole, it was certainly one of the most diverse and interesting of the time. If Mr. Ziegler, as I've said, does it slightly more than justice, that is distinctly better than doing it less. No reviewer will risk rebuke for recommending the result.