Harold S. Geneen did not lose many internal battles in the nearly two decades he ran International Telephone & Telegraph Corp.

But in what appeared to be his last major confrontation, in 1977, Geneen appeared to have lost big.

Tainted by scandals surrounding the company's acquisition of the Hartford Insurance Co. in 1970 and the company's role in helping overthrow Chilean President Salvador Allende, Geneen was forced to relinquish the title of chief executive of ITT.

Although he remained as chairman - a title he still holds - Geneen also failed to convince the board to pick his favorite, Rand V. Araskog, to Succeed him as chief executive.

Instead, the directors chose Lyman C. Hamilton Jr., a financial whiz who came to ITT from the World Bank in 1962.

On Wednesday, however, Geneen demonstrated that while he may no longer hold all titles, he again is back in power.

Hamilton, who sought to dismantle some of the overseas empire Geneen created, was ousted as ITT chief executive. And Araskog replaced him at a long board meeting which Hamilton did not attend.

Unlike most other corporations, ITT was nearly synonymous with its chief executive. Probably no other corporate leader, save Armand Hammer at Occidental Petroleum, made a more personal imprint on the company he headed.

The ascension of Araskog late Wednesday, analysts said, means a return to the management style of Harold Geneen, a style that thought bigger to be better.

Hamilton had spent much of the 18 months he headed the company (he spent most of 1977 as president while Geneen continued as chief executive) trying to reduce some of the conglomerate's European holdings, while at the same time carrying out a Geneenera strategy of posturing ITT as an important force in the U.S. communications and information-rpocessing industries.

"It had to be the restructuring of the European operations that was Hamilton's downfall," said one analyst today. "That was the only area of contention within the company."

"If an operation was losing money, Geneen would say, 'let's get the right guys and lick it'," noted Harry Edelson of Drexel Burnham Lambert Inc. "Hamilton would look it over and if it did not make sense, he'd say, 'Let's get rid of it'."

Unlike Hamilton, 52, who came up through the financial side of ITT, 47-year-old Araskog was a technology manager. He joined ITT in 1966 as a vice president of its Federal Laboratories and the next year became president of its defense communications division.

In 1971 Araskog was named to head what is now called the ITT Telecommunications Group-North America. When Hamilton became chief executive, Araskog was named senior executive vice president and chief operating officer under Hamilton. CAPTION: Picture, RAND V. ARASKOG . . . Geneen's choice at ITT