The strong tide of pacifism sweeping across Europe and the growing importance of the Mediterranean theater are causing NATO leaders to rely more heavily than ever on Italy.
The thinking in political circles in Rome is that despite the first signs of a significant pacifist movement here, Italy will remain unwavering in its support of NATO, the United States, and the deployment of 112 nuclear missiles in Sicily as long as the US continues to push for disarmament.
The arms limitation negotiations scheduled to begin Nov. 30 between the US and the Soviet Union have been the key factor in obtaining Italy's willingness to deploy the land-hugging nuclear cruise missiles. ''It lets the pressure off the government a little,'' said a senior Defense Ministry official, referring to both public opinion and internal politics.
Italy's Socialist Party, which until recently has usually been in the opposition, approved the missile decision with the disarmament talks caveat in 1979. It would now be extremely awkward for the Socialists, who are part of the ruling coalition government, to reverse their position on the missiles, even though Socialist rhetoric in recent weeks has indicated a growing coolness to the US.
An estimated 200,000 people turned out Oct. 24 for the peace march in Rome just as they did in London, Paris, Oslo, and Bonn. But the Italian demands for peace were distinctly less unilateral and less radical than those of the other European pacifists.
The demonstration was clearly aimed at the Soviet Union as well as the US. The march wound past the Soviet Embassy as well as the American Embassy, and the slogans and placards protested the Soviet-built SS-20s as well as the American cruise and Pershing missiles.
Italy's three most powerful trade unions, including the one dominated by the Communist Party, have recently called for balanced arms reduction toward the zero option, which prompted one peace march organizer to complain, ''They're moving toward the NATO position, not away from it.''
Prime Minister Giovanni Spadolini, who claims credit for having, along with Germany, convinced Washington to agree to the zero option goal of total bilateral disarmament, said in an interview published Oct. 26, ''I refuse to believe that the peace movements flourishing in many countries really want a neutral Europe.''
Italy's continued staunch support of the alliance is particularly crucial at this time. Italy is leading the European allies in defense budgeting. Despite an inflation rate running between 18 and 20 percent and a public spending deficit as large as that of the US, Spadolini's new budget for the next fiscal year increases defense spending almost 29 percent - 8 percent in real terms. It does not appear that any other NATO ally will even meet the 3 percent annual growth requested by NATO to bolster conventional forces that would meet the first shock of an attack.
More important, Italy's decision to deploy the cruise missiles paves the way for Germany to accept its portion of the 572 cruise and Pershings planned by NATO. Germany has said it would take the nuclear missiles only if another continental ally will also. So far, the other countries in the program, the Netherlands and Belgium, have not made this commitment, nor do they appear likely to.
''When the missile program first came up, the Americans thought the Italian government would have a real fight on its hands,'' said a US diplomat here, ''and we were quite surprised when the Italian reaction was that it was quite manageable.''
A sense of vulnerability is the primary motivation for Italy's strong commitment. ''We looked at the threats to Italy, both from the Soviet military buildup and from instability in the Mediterranean, and we have decided that Italy has to do its share,'' a senior Defense Ministry official said.
Since 1978, the Sovied Union has lined up 250 long-range nuclear missiles along its border, any one of which can reach Italy. The study ''Soviet Military Power'' recently released by the US secretary of defense said there is evidence that the pace of SS-20 base construction has increased since January 1981, and that another 65 launchers with 195 nuclear warheads will soon be deployed.
Italy would also have trouble defending itself in a conventional warfare attack. ''Italy recognizes that the alliance is the only protection and hope she has. The Italian Army couldn't fend off a serious invasion by itself,'' said a NATO expert.
Italy is also responding to the gradual shift in the crisis area from Central Europe to the Mediterranean. ''In my opinion, the placing of missiles is more justified in the context of a North-South confrontation than in the East-West context,'' said Socialist deputy Falco Accame. Italy is the strongest of the three NATO countries in the southern flank, and must be ready to fill the gaps in the conventional NATO defense in the event the US needs to deploy some of its NATO forces outside the treaty alliance boundaries.
But it also worries about a new threat on the southern flank with the injection of Soviet arms there and the general instability in the entire region. Defense Ministry officials do not believe that Libya's leader Muammar Qaddafi has given the Soviet Union permission to use Libyan bases, but they do not exclude the possibility of this occurring at some time in the future.
Qaddafi threatened to bomb NATO bases that would house the nuclear missiles, including the one being built in Comiso, Sicily. But Italian officials in both the Foreign and Defense Ministries are not taking the threat too seriously.