India’s militarily explosive border with East Pakistan lies several hundred yards from the small frontier of Boira, where a smiling young Indian Army lieutenant stood in ankle-deep mud gesturing toward the frontier. "I will not be going with you," he told a half-dozen foreign journalists about to set off on foot across the frontier. "International law says we must not cross the border." The officer repeated this stilted comment several times for the correspondents he had escorted through Indian Army lines to Boira. He had evidently eagerly rehearsed his words, which reflects India’s sensitivity to events in East Pakistan and India’s disputed role in them.

The Indian lieutenant passed the journalists on to a wizened man of perhaps 60 who carried an old carbine, identified himself as "Mukti Bahini" - the guerrilla military arm - and then set off at a brisk pace through a drenching rainstorm. Floundering in the thick mud, the journalists followed him on a twisting four-mile hike through rice paddies and beside a border marker dividing India and East Pakistan. At the end of the march was an abandoned school house, now identified by a banner as sub-sector headquarters for the "Liberation Forces of Bangladesh." Major Najmul Huda, a 33-year-old precisely spoken man who said he had been a captain in the Pakistani Army, asserted that from the school house he controls an area of 150 square miles. He has a company of about a hundred regular soldiers who defected to the rebel cause, and 7,000 villagers trained by his forces. The guerrillas claim to have implanted such headquarters throughout East Pakistan, and say they are intensifying an insurgency that will drive the regular Pakistani Army from the territory in a year or so.

It is impossible to judge the validity of their claims on a quick hike in and out of the rebel zone. But impartial analysts credit the guerrilla organization with having expanded within seven months from zero to a force of 80,000 to 100,000 men, a figure roughly equal to the number of regular Pakistani soldiers deployed against them. These analysts feel that the Mukti Bahini may be developing from a rag-tag, hurriedly thrown together force into something of an organization with increasing capability for coordinated actions. Authoritative reports circulating on the diplomatic community here also support Major Huda’s assertion that the Mukti Bahini has "become more aggressive and offensive within recent weeks." In the past 20 days, rebel attacks concentrated on communications and logistics lines show a pattern of increasing sophistication in the guerrilla’s arms supplies and training, according to these reports, which add to the speculation that India may have recently stepped up tactical support for the guerrillas. They have been helped by the dispersal of Pakistani troops around the frontier over the past two weeks.

The guerrillas’ success in the interior has apparently led to increasing retaliation by Pakistani forces against Indian border areas suspected of harbouring them. There are daily reports of shelling of villages and in a few cases Indian areas are said to have been strafed by Pakistani aircraft. Boira is in an area that was shelled last week. All indications are that the Indian troops camped there have not crossed into East Pakistan to help the guerrillas. Whether they support them in other ways is a matter of bitter dispute. While the Indians deny that they do. Pakistan as a matter of routine describes the guerrillas as Indian agents or puppets.

Major Huda denied that his men receive arms or training from the Indians. He attributed what he described as a significant increase in the number of weapons available to his men in the past few weeks to the increased capture of rifles distributed by the Pakistani Army to loyal civilians. But there are persistent reports that a major influx of new arms began coming into the Indian border areas about 10 days ago. According to one version, which cannot be confirmed, Indian arms deliveries were stepped up after the Soviet Union assured India that it would replenish Soviet weapons sent on to the rebel forces.

Wounded guerrillas are sent across the border into India for medical care, and the villagers in his area receive food from the Indian Red Cross and from Oxfam, Major Huda said. The guerrillas and the Indian military also undoubtedly exchange intelligence. Observers feel that official leaks in New Delhi to the Indian press, confirmed by reliable Indian sources here, show a detailed knowledge on the Indian side of the positioning of Pakistani forces throughout the country. The apparent growing cohesion within the Mukti Bahini and the emergence of officers like Major Huda as de facto district administrators are trends that are being carefully scrutinized by Western observers.

"Some of us assume that East Pakistan will in fact be an independent country at some point," says one Western diplomat. "We don’t know if it wiH take six months or six years. But if it does happen there will be a new generation of leaders to have been formed in the guerrilla battle, and it will be important to know what they are."