In December 1941, Japanese forces swarmed into Lower Burma, determined to seize the British colony and control the vital Burma Road linking Rangoon with China. Aided by Burmese nationalists seeking independence from Britain, the Japanese rolled up a string of victories in some of the bitterest fighting in World War II.

Today, despite the harshness of their rule in Burma 40 years ago, the Japanese have managed to maintain an economic inside track here. Their role in Burma is the more remarkable because this is considered one of the most isolationist countries in the world.

Moreover, the Japanese presence here is unusual in that it seems to have arisen to some extent because of Japan's wartime role rather than in spite of it.

With an outlay of roughly $200 million a year, Japan is by far Burma's largest foreign aid donor.

The Japanese community in Burma numbers about 400 persons, more than any other nonimmigrant nationality. The Bank of Tokyo is the only foreign bank permitted to operate here.

Among the many Japanese industrial projects turned over to the Burmese--no foreign investment is allowed--have been plants to assemble 2,000 Mazda cars and Hino trucks and buses a year.

In the latest measure of Tokyo's involvement here, a consortium of Japanese companies signed an agreement with Burma to explore for oil in the Gulf of Martaban.

In one of the few such agreements since Gen. Ne Win embarked on his "Burmese way to socialism" campaign following his military coup in 1962, the Japanese firms signed a contract Feb. 5 to drill two offshore wells starting later this year at a cost of about $18 million, according to Western and Asian diplomats.

"I think this is an investment for the future," a Western diplomat said of the oil exploration agreement. "There's no immediate return" on much of the Japanese aid to Burma, "but the Japanese are thinking of the long term, and Burma's potential is great."

"The Japanese are investing in a source of supply," another Western diplomat said. He noted that Japan's aid started out as war reparations, but now has "gone beyond that to the economic interests they perceive . . . ."

A Japanese observer attributed Burma's special relationship with Japan to the role the Japanese played in ending British colonial domination here and, in a way, furthering Burma's independence.

That role goes back to early 1941 when the Japanese Army formed a clandestine organization to aid Burmese nationalists agitating for independence from Britain. Known as the Minami Organ, the group was formed to mobilize Burmese nationalists to support an eventual Japanese attack on the British. Among the people recruited was Shu Maung, who became better known as Ne Win, which means "rising sun" in Burmese.

The recruited Burmese nationalists formed the Burma Independence Army, which Rangoon portrays as having played the central role in battling colonialism and recovering Burmese sovereignty.

"Through the training that Ne Win and other military leaders had in Japan, they've kept a very special attachment to Japan," the Japanese observer here said. "To some extent, the Minami Organ helped Burma gain independence."