Calcutta-Crossing the border into "Bangladesh"-"Bengal Nation," as most East Pakistanis now call their region-you feel you're seeing something filmed a long time ago by some newsreel pioneer. The ancient Enfield and Garand rifles in the hands of the overnight revolutionaries, the refugee-laden carts, the bodies lying unnoticed by the roadside -all this could be out of the Spanish Civil War or the Chinese revolution.

A "Liberation Army" lorry with a dozen "freedom fighters" and two or three rifles among them takes you along the road to the Bengalis proudest possession in this part of the region-the city of Jessore, 30 miles from the Indian border, wrested from the Pakistani army in bloody fighting. Before entering Jessore you pass several razed villages. Bodies lie in the charred ruins. The ruins in the heart of Jessore suggest that the West Pakistani air force has not been too careful.

Only a few months ago, people in East Pakistan would complain to visiting journalists of the "dirty and arrogant Hindus." Now they say, "Hindu, Moslem, that does not count any more. We arc all Bengalis." The enemy now is "Punjabi", the most commonly used name for the West Pakistanis.

The villages are plastered with slogans, the quotations from Rabindranath Tagore, the great poet of pre-partition India, sorting oddly with the exhortations of Mao Tse-tung: "Long live the people s war!" "Political power grows out of the barrel of a gun." The Maoists are one of the three organized groups in East Pakistan. They are still only a tiny minority compared to the two dominant groups-the Awami League party of Sheikh Mujib and the Bengali units of the army, totaling about 25,000 menbut their strength is growing. Sheikh Mujib, who is enormously popular (and known for his opposition to violence) is either dead or in jail.

HOW IT BEGAN

No one we talked to seemed to have expected the situation to come to this anachronistic killing of poor people by other poor people united for 20 years by religion and a common national ideal. In Chuadanga, a town 20 miles from the border serving as the "provisional capital of Bangladesh," Maj. M. A. Osman. military commander of the Southwestern Sector, told us how it had begun for him.

On the night of March 24, when the "Punjabi" army cracked down. Major Osman had a discussion with his Punjabi commanding officer, Major Attaquc Shah. "He was extremely polite, and let me keep my jeep, my gun and my driver." Next day Sheikh Mujib appealed to the Bengalis to rise up against the "occupiers," and Attaque Shah had to be arrested and, later on, liquidated."

What will this tragic new enmity-the product of short-sighted refusal of autonomy that can only profit the extremists in both halves of Pakistan-lead to? For a certain Dr. Haque, Major Osman's political deputy, a bearded man in a green sombrero who fondles his two 45 caliber guns as he talks and is almost the perfect caricature of a revolutionary leader, the answer is "very simple."

"There are 72 million inhabitants or more in Bangladesh," he says, "In this human ocean there are still Pakistani pockets. In order to win, since there are less than 100,000 Pakistan soldiers in Bangladesh, each Punjabi would have to kill about 1,000 Bengalis. This is obviously impossible, and therefore our victory is certain."