On the first day of what is called here "The Battle of the Malvinas," Buenos Aires was blacked out by the ruling military's order.

The measure seemed somewhat curious, despite the heavy fighting reported off the Falkland Islands, known here as the Malvinas. In geographical terms, it was roughly equivalent to blacking out Washington during an air raid on Puerto Rico. In strategic terms, it appeared puzzling.

But as Argentina plunges into its first international conflict in 112 years, blackouts in Buenos Aires are only part of what has appeared to be an elaborate effort by the military government to shape the mood of this restless, uncertain country.

This effort reflects a long Argentine history of placing importance on outward public display rather than accuracy.

In recent days, television and radio stations have been silenced for deliberate intervals as a military "exercise." Civil defense instructions have been broadcast. Newspapers have been told to avoid accounts of everything from Argentine military movements to the weather in the South Atlantic.

The military's reports from the war zone have sharply differed from those of Britain. While Britain has claimed no losses in this week's fighting, Agentina has insisted that half of Britain's carrier-borne Air Force has been destroyed, and several of its ships badly damaged.

And, by Argentina's account, the British garrison on the island of South Georgia is still under pressure from specially trained Argentine commandos who have been hiding out amid the mountains and glaciers.

The wildly variant military dispatches--just as the seemingly extreme security measures in Buenos Aires--appear to be best explained in the ruling junta's own words: Argentina's conflict with Britain is not only an intercontinental shootout, but a "psychological war."

Britain, according to daily reports by the military command, has been waging psychological aggression against Argentina's morale for weeks. And although Argentina's military may not have much experience at conventional armed conflict, its leaders, by their own account, are veterans of the battle of the mind.

Since seizing power in a 1976 coup, the military here has frequently charged that Argentina's moral values have been under assault, both internally and abroad, by the forces of international communism.

For the military, these forces have included human rights groups who have charged Argentina with frequent violations and who, the military has said, are often communists conducting a propaganda campaign.

The government has responded to this perceived threat with vigorous efforts to keep influences considered subversive out of Argentina and an extensive "educational" campaign of its own.

Now, the government says, Argentina faces the same threat from the "flagrant lies" of Britain over the state of the Falkland Islands and what has happened in the South Atlantic during the past week.

The response by the government has been a vigorous psychological counterattack that has reflected both its long-held distrust of all that lies outside its realm and its jealousness over information in a sophisticated, politicized society.

For the military here, the psychological struggle begins with accounts of the fighting 400 miles off Argentina's southern coast in the Falkland Islands. Argentina has banned all but state news service journalists from the captured territory, and thus has eliminated most means of impartial reporting.

As the fighting grew heavier this past weekend, the discrepancies between British and Argentine accounts seemed to grow wider and wider. While neither side seems to be able to prove the accuracy of its claims, some of the reports offered by military officials here in recent days have seemed distinctly doubtful.

Last night, to back its claim that the crucial Falklands airfield outside Port Stanley had not been damaged, military officials showed on television and in a special press room a film they said had been taken late in the afternoon at the airport.

Shot from the window of an aircraft, the film showed a spotless runway surrounded by clear fields unblemished by craters.

But there were problems with this film. It showed blue skies above the small airport, though widespread reports said clouds partly covered the Falklands yesterday. There were no signs of the airstrip buildings the Argentines said had been damaged, nor the oil drum that was reported to have been set ablaze, and foreign television correspondents argued to military officials that the film looked precisely like one that was released here earlier this week.

By this morning, military sources were telling Argentine news services that some damage had been done to the airstrip, but that it had been repaired quickly.

Apart from the military communiques, military officials here during the past week have filled the ears of both Argentine and foreign journalists with lively--but inaccurate--accounts of the South Atlantic conflict.

The junta has warned journalists not to stray from its official reports. But despite warnings of official sanctions, the reports continue to appear, provided by officers in military headquarters who offer information provided they are guaranteed anonymity.

In one notable case earlier this week, reports suddenly surfaced that a British destroyer, the Exeter, was in trouble off the island of South Georgia. Relying on "highly responsible" sources, Argentine wire services here first reported Wednesday afternoon that the Exeter was in trouble, then that it was afire.

By midafternoon, the Exeter appeared to be in a grave state, simultaneously devastated by a mine, rocket fire from Argentine commandos, and a ballistic missile, according to various reports broadcast on Argentine radio and wire services.

Then, suddenly, the reports disappeared, along with the Exeter. British officials said that it was nowhere near South Georgia, and the wires canceled their bulletins without explanation. Military officials later hinted that this, too, was part of the British psychological assault.

A series of such incidents has left many journalists and citizens here in a perpetual state of uncertainty over the critical military conflicts in the oceans to the east. At the same time, the government has issued a constant barrage of reminders that Argentina is at war and that great sacrifices are required.

While military information is restricted to communiques from the junta or joint chiefs of staff, radio and television stations emit a constant stream of patriotic advertisements, songs and films. Argentine forces are shown marching down the streets while jets stream overhead; an Argentine boxer is pictured knocking an opponent out of the ring.

On radio stations, Argentine celebrities are quoted at regular intervals supporting the April 2 invasion of the Falklands, followed by a ringing martial anthem celebrating the islands, "which always were and always will be" Argentine.

By midweek, political leaders here were quoted as complaining that not only were they learning little from government officials, but they had to find out the news of Britan's assault on South Georgia from Uruguay, whose stations continue to broadcast international reports.

But for the military authorities, the scant information--like the practice blackouts and civil defense warnings--are all part of preparing Argentina for what is to come.

"The loyal completion of daily responsibilities by every Argentine," one military statement put it this week, "constitutes the greatest support to the Fatherland and the key to victory in this decisive hour."