Three things could have prompted Argentina's surprise invasion of the British-ruled Falkland Islands. The three are: politics, oil, and opportunity.
Politics. Argentina's military junta made its move at a time of increasing domestic unpopularity. Its cautious political reforms have not satisfied the public, which appears to favor a return to democracy.
The military is also being blamed for Argentina's economic problems.
Local observers suspect that behind the junta's decision to invade the Falklands was the wish to distract public opinion by stirring up nationalist fervor.
The junta has mounted a huge propaganda campaign to present the invasion as the courageous recovery of land that was legally Argentine. As the scenes of flagwaving and rallies showed over the weekend, the campaign has caught the imagination of many Argentines.
Oil. Argentina, like the rest of the world, is thirsty for oil. But Argentine oil-drilling has been disappointing. Waters around the Falklands, about 400 miles off the Argentine coast, may be rich in oil - perhaps richer than the North Sea fields between Britain and Norway.
Eighteen months ago, Argentina advertised for oil prospecters to explore an area extending into the Falklands waters. Britain protested the move. Some experts believe the Falklands area contains about 2 billion barrels of oil, which would be worth about $60 billion at current market prices.
Opportunity. Two weeks ago, Argentina found itself with an excuse for action. A group of Argentine scrap merchants landed on uninhabited South Georgia Island, a dependency of the Falklands. They hoisted the Argentine flag and began dismantling an unused whaling station.
Britain protested and dispatched a naval ice-patrol ship, Endurance, to ensure that the Argentines were expelled.
But Argentina immediately upped the stakes. It reasserted a claim to sovereignty over the islands, saying Britain illegally seized them from Argentina in 1832. Then it sent in warships to defend the scrap merchants. Finally, on April 2, it invaded the Falklands with several thousand marines.
It appears that Argentina's junta had set itself a deadline of the end of the year -- the 150th anniversary of British rule -- to take back the Falklands. Observers think it is likely that the South Georgia Island incident gave Argentina an excuse to accelerate the timetable.
The Argentine military regime had publicly grown increasing irate with British diplomatic ''foot dragging'' ever since serious negotiations began in 1977 on the two countries' conflicting claims of sovereignty. At the end of February, a round of talks ended in deadlock and Buenos Aires warned then that unless there was rapid agreement it would ''seek other means to solve the dispute.''
The British position has always been that the handing back of the Falklands could not be a desk-clearing exercise imposed by Argentina. It says a settlement must be worked out patiently and must take into full account the wishes of the 1 ,800 people inhabiting the Falklands, 97 percent of whom are British stock.
A agreement signed 10 years ago established airline and telephone links with mainland Argentina and licensed the state oil firm to supply fuel to the islands.
But these measures did not win over the islanders. Port Stanley, the islands' capital, with its pubs, Tudor-style town hall, and governor's London taxi has always reflected British sentiments.
On a visit to the islands in 1980, a British Foreign Office minister, Nicholas Ridely, warned that Argentina's patience was running out and that there were two months at the most to come up with a concrete proposal. He strongly suggested a compromise involving the ceding to Argentina of titular sovereignty over the islands in return for full rights there for many years -- a kind of Hong Kong solution. But the islanders reportedly turned this down.
Britain has been examining other solutions, but this has not satisfied Argentina. One such solution is to create an economic zone for Argentina and the Falklands. The two would cooperate fully on economic matters, but political control would remain with the British.
Britain's stern reaction to the Argentine invasion poses a problem for Argentina. Britain has raised the possibility of a direct confrontation between Argentina and Britain, which Argentina would almost certainly lose if Britain really was prepared to use all its available resources.
The decision of the Security Council also implies that Argentina may risk growing international isolationism if her troops remain in the Falklands.
The junta also runs the risk of losing the political mileage it has gained domestically if it now backs away from the ''national enterprise.'' Many Argentines would see a withdrawal as a defeat that could finish the regime politically.
Britain, however, is under pressure from the US to find a diplomatic solution.
In the days ahead Washington's mediating role between two of its closest allies is likely to intensify.