London — Britain is fighting its Falklands war on two main fronts - a bite-by-bite military campaign in the wintry South Atlantic, and a gathering effort to reassure an apprehensive public opinion in homes, offices, pubs, and clubs here at home.
On the military front, the Margaret Thatcher government was jubilant Sunday. It said it had conducted two successful air attacks against the airstrips at Port Stanley and Goose Green, both on the island of East Falkland.
Harrier jump jets from the task force carriers and Vulcan bombers from Ascension Island, backed up by naval gunfire, were said to have cratered both airstrips and jolted Argentine defenses. No British lives or aircraft were reported lost.
On the home front, a new poll confirms that most (three out of five) people questioned oppose losing any British lives whatsoever. Meanwhile, the opposition political parties clamor for a pause in military action to allow Foreign Secretary Francis Pym's latest diplomatic sally to the United States to bear fruit.
But the diplomatic front, though still pursued by Mr. Pym, seems to have less momentum at the moment than the other two. On the domestic political front, for instance, the prime minister moved to defuse criticism May 2 by offering secret briefings on diplomatic (but not military) moves to opposition party leaders after Mr. Pym's return. The leaders would not be able to reveal in public what they had learned.
In the South Atlantic, the government strategy is gradually to escalate military pressure on Argentina by isolating the Falklands from the mainland - while losing as few British lives, aircraft, or ships as possible.
Informed sources here say the overall British aim is to enforce the total sea and air blockade, which was imposed May 30, and to occupy the Falklands (perhaps starting with the west island) piece by piece. If necessary, this could culminate in an all-out attack on Port Stanley itself on the East Falkland island - but only, it is suggested, after the naval task force has been reinforced by extra men and aircraft now on the high seas several days away from the war zone.
Before that point is reached, however, London hopes that Buenos Aires will be forced to agree to withdraw its forces from the islands. Mrs. Thatcher says the withdrawal could be supervised by the United States or the United Nations.
For the moment, Argentina appears to be holding firm and to be ready to fight on. But Britain is counting on Argentine public opinion turning against the military junta, especially as Argentine inflation, now about 150 percent a year, is worsened by West European and just-announced (and more modest) US and Japanese sanctions.
Britain's capacity to wage a long naval campaign has been improved by the promise of US logistical support. Mrs. Thatcher is said here to be greatly heartened by the prospect of US tankers refueling her own task force ships and giving other logistical support as indicated by Washington April 30.
British officials insisted May 2 that the two attacks on Port Stanley airfield and the Goose Green airstrip the previous day had been successfully completed without loss. The Defense Ministry flatly contradicted Argentine claims that at least five Harrier jets had been shot down. Spokesman Ian McDonald told newsman that only one task force aircraft had been slightly hit and had already been repaired. (It is also understood here that Britain also denies Argentina's claims that British troops tried to invade the Falklands three times on May 1.)
The Ministry of Defense added May 2 that one naval frigate had suffered superficial splinter damage from Argentine air attack and one man, Able Seaman Ian Bricknell of Devon, had received minor wounds but was still able to walk.
The spokesman would not say how many Vulcan bombers flew from Ascension Island 3,000 miles north to bomb the airstrips early on May 1. The Vulcans would have required at least two in-flight refueling operations for such a distance. The spokesman confirmed that Harrier jets had carried out a second attack later in the day to reinforce the first bombing and to stop Argentine troops from repairing the airstrips.
In the attack by Argentine fighters and bombers against British aircraft and ships, the British claimed that one Argentine Mirage supersonic fighter and one Canberra bomber had been shot down by British planes. Another Canberra bomber was said to have been severely damaged. In addition, it was believed that the Argentines' own groundfire had shot down another of their Mirage jets.
It is important for Mrs. Thatcher to be able to keep on announcing apparently successful operations like this one, especially ones in which no British lives are lost.
Since Argentina invaded the Falklands April 2, British public opinion polls have shown strong support for the Thatcher strategy. But they have also indicated that at least 50 percent of the people are opposed to losing a single British life to regain the islands.
A new poll released May 2 in the Sunday Times newspaper (carried out the day before the attacks on the Falkland airstrips) showed that the percentage had risen to three out of five. Only one in seven was prepared to see 100 or more servicemen killed.
Findings like this put strong pressure on Mrs. Thatcher to go slowly in the Falklands, to keep using air and naval power rather than an amphibious landing against the estimated 3,600 Argentine men defending Port Stanley itself. The total Argentine force on the islands is reckoned to exceed 10,000 men.
A small advance party of naval commandos is said to have been landed somewhere in the Falklands since April 29. Informed sources here expect one of Mrs. Thatcher's next moves will be to seize territory on West Falkland - perhaps in the region of Fox Bay - which is defended by only about 900 Argentine troops.
Significantly, a majority of people now seem to disapprove of one of Mrs. Thatcher's key diplomatic points: giving the Falkland Islanders themselves the right to determine any settlement. Seventy-two percent of persons polled for the Sunday Times said the government should take into account ''the interests of Britain as a whole'' and only 24 percent said they should rely on the wishes of the islanders.
Although 7 out of 10 people supported Mrs. Thatcher's actions so far, it is clear that this support has depended in part on the absence of British casualties.
Meanwhile, the opposition Labour Party is deeply divided by the conflict. Party leader Michael Foot on Sunday delayed his response to Mrs. Thatcher's offer of secret diplomatic briefings. To accept it would tie his own hands in future House of Commons debates.