The announcement that Britain has suffered its first major losses in the war in the South Atlantic has dramatically changed the nature of London's effort to regain the Falkland Islands and may cost the government public support here at home.
A grave-voiced Ministry of Defense spokesman appeared on television screens late May 4 to reveal that the destroyer Sheffield, 3,660 tons, with a crew of 270, had been hit by Argentine fire within the maritime exclusion zone, and had been set alight.
Its crew had been ordered to abandon ship. All who had escaped had been picked up but the spokesman said it was feared there had been ''a number of casualties.''
It was later learned that an Argentine air-to-ship missile had scored a direct hit on the Sheffield's control room.
Details were sketchy. But the spokesman went on to say that a British Sea Harrier aircraft had also been lost--shot down during the most recent bombing raid on the Falkland Island airstrips. The pilot was killed.
This was the kind of news Prime Minister Margaret Thatcher has been trying to avoid. British public opinion has supported the dispatch of the task force to the South Atlantic but a majority has opposed any British loss of life.
Britain's earlier sinking of an Argentine naval warship, the cruiser General Belgrano, had already moved the confrontation in the South Atlantic to a new phase.
Britain was forced onto the defensive as criticism of the sinking of the Argentine cruiser General Belgrano grew in the House of Commons, and in Paris, Bonn, Brussels, Dublin, and other European capitals.
The Labour Party opposition here at home feared that the Argentine junta was about to try to regain credibility by retaliating with a big surprise attack on British ships.
Even so, London stood firm. It robustly defended its action and hinted at a landing on the lightly defended West Falkland Island by announcing late May 4 new air attacks on Port Stanley and Goose Green air strips on East Falkland.
These new attacks, according to Defense Minister John Nott, were designed to render old strips unusable by three types of aircraft operating within the Falklands themselves: communications, light supply, and ground attack.
Grounding such aircraft would be a prerequisite before British Marines moved ashore to seize remote parts of the Falklands and increase military pressure on the junta in Buenos Aires.
Previous air attacks on May 1 had prevented the airstrips being used by heavier Argentine transport aircraft flying from the mainland.
A small detachment of British reconnaissance commandos is believed to have been somewhere on the Falklands for almost a week.
The sinking of the General Belgrano, however, illustrates the enormous international and domestic difficulties under which Prime Minister Margaret Thatcher is attempting to push Argentine troops off the island.
Although loss of life was not as great as at first feared, the horror of conventional naval war--long overlooked in the nuclear age since World War II--moved to front and center stage.
Britain, Europe, and the United States came face to face May 4 with the tragic prospect of hundreds of Argentine sailors fighting for survival in the icy, mountainous, winter waters of the South Atlantic.
British public opinion supports the show of British force to support diplomacy. It is far less enthusiastic about the actual use of that force. A majority is opposed to any loss of British lives.
The world has not seen a full-scale naval campaign since World War II. Both Korea and Vietnam were essentially land battles.
At first, as British reports affirmed, it was an Argentine submarine put out of action, then two Argentine aircraft shot down and two damaged, then one patrol vessel sunk and another damaged. With the successful initial bombing of Port Stanley airport, Britain was in a confident mood.
The sinking of the Belgrano raised many thorny questions. British people who had supported Mrs. Thatcher until that point were upset at the thought of bodies in the water and young men dying, even though they were on the enemy side.
Labour Party leader Michael Foot and foreign affairs spokesman Dennis Healey repeatedly asked in the House of Commons May 4 whether it had been necessary to sink the cruiser rather than to disable it, and whether the decision had been under political or military control.
Mr. Healey asked whether the sinking was consistent with the government's declared policy of using ''minimum force.'' He asked how far out of the exclusion zone the cruiser had been when attacked, and how far away it had been from the British task force.
The government case, put by Prime Minister Thatcher, Foreign Secretary Francis Pym, and Defense Minister Nott was that torpedoing the cruiser had been necessary even though it had been 35 miles out of the zone.
Mrs. Thatcher regretted Argentine loss of life but insisted that her first duty was ''to protect our own boys.''
At one point Mrs. Thatcer said, ''If we had waited any later, it would have been too late and some of our ships might have been sunk.''
Britain, she said, was still pursuing a diplomatic settlement through proposals made by Peru. Morning papers here May 4 reported that Argentina had already rejected the proposals. Argentina had broken the peace, Mrs. Thatcher said, and Argentina could end British naval action by withdrawing from the Falklands.
Mr. Pym said that the action against the cruiser ''was as inevitable as it was right.''
The prime minister and Mr. Nott stressed that the cruiser had posed an ''obvious'' danger to the British forces. It had been armed with 15 six-inch guns with a range of 13 miles. It had been, Mr. Nott said, ''closing on elements of our task force which had been ''only hours away.''
Two escort destroyers had carried Exocet surface-to-surface missiles with ranges of over 20 miles. The danger had been so grave that the task force commander could have ignored it ''only at his peril.''