Yesterday’s treaty of “friendship, peace and cooperation” between New Delhi and Moscow raised, ironically, only the prospect of more enmity, war, and disaster for the subcontinent. So also does Yahya Khan’s incredible decision to start the secret military trial of Sheikh Mujibur Rahman this week. India and Pakistan are running out of all options but open conflict fast. While Mujib festered, incommunicado, in a West Pakistan prison there was at least the slim chance that Islamabad might retrieve its senses and - overthrowing discredited policies - do business with the elected, unchallenged boss of Bangladesh. His impending trial with inevitable verdict, strangles that chance. While Yahya could invoke the strong possibility of Chinese intervention against Mrs. Gandhi there were restraints on Indian military action. Those restraints are far weaker after the newly negotiated Gromyko pact with its pointed reference to possible “attacks or threats” and joint “effective measures” to remove them. Who could threaten such attacks? Only China if fighting broke out along the East Bengal borders. And will even China risk it now, with her own borders sore and sensitive to past Soviet clashes?

No one accuses the Indian Government of warmongering. But feelings in the land are running high, as yesterday’s massive demonstration showed. Political pressures to strike are immense. Crucially, economic pressures to find a final answer seem irresistible. A permanent burden of six or seven million refugees cannot be supported for long - especially since world aid has proved so puny. Either the millions must go back freely to a Bangladesh regime they trust (the Mujib solution); or they must be ushered back by Indian troops to a territory conquered and guarded by Indian troops.

The calculations any Indian general may make are all too fatally attractive. Let sealed amity with Russia, plus a gambler’s throw, divert divisions from northern borders to the Punjab so that Pakistan faces military stalemate on the plains; then take the army in the East apart - by paratroop drops on airports, by naval blockade, by frontal assault on an Islamabad force spread thin and far from reliable supply lines. There are Awami League leaders in Calcutta who would be charmed to retrieve power this way; every gauge of Bengali opinion available indicates that a vast majority of East Pakistanis would welcome the invaders as liberators - provided they got out quickly once Yahya’s army was confined to the West.

It is an ominous scenario. A scenario clouded by blood-letting, full of risks and incalculable furies. But can it be stopped? Only if world opinion can somehow change Yahya’s course. Only if Mujib is not condemned. Only if India is given massive and effective help to stave off the ultimate day of despair. Can it be stopped?