It is the most overworked of phrases, distinguished this time by the probability that it is true: 1983 will be a ''crucial year'' in the superpower struggle to control the nuclear arms race.
Moscow and Washington are conducting two parallel negotiating processes in Geneva: the first, on long-range, strategic weaponry; the second, dealing with shorter-range nuclear armaments based on the European continent.
In recent weeks the new Kremlin leadership, while making no startling departures from past negotiating positions, has issued major policy statements on both sets of talks. On European arms, party leader Yuri Andropov has significantly refined the Soviet position to include an explicit public offer to remove ''dozens'' of late-vintage SS-20 Soviet missiles from the European part of the country.
The US administration, too, has been devoting more public attention to the arms talks - but so far it has broken no new substantive ground.
Even in the best of circumstances, the world will not be a strikingly safer place 12 months from now. ''Euronuclear'' forces could be limited significantly, but not completely, by this year's talks. The two sides' sharply divergent strategic-arms reduction proposals envisage phased cutbacks that would leave thousands of more potent nuclear warheads untouched at least for the foreseeable future.
At issue for now are these relatively modest aims: ensuring that the world does not get appreciably more dangerous, and trying to strengthen barriers against accidental launch of weapons that neither side, in a rational moment, would dream of using.
Rarely if ever since the outset of the arms negotiation process some 15 years ago has each of the superpowers had such evident incentive for negotiating. This is especially true on the European front, where there may be something approximating a ''deadline'' for compromise. The Western alliance is publicly committed to start deploying new US missiles by the end of 1983 to counter the Soviet missile force.
Yet the hitch - one that should become increasingly evident throughout the year - is that the two sides' incentives differ, and that alongside incentives to negotiate there are potential disincentives to make the concessions that are key to workable compromise.
And there are complicating historical differences between the strategic nuclear forces of the two superpowers. The Kremlin has long relied on large numbers of powerful, land-based intercontinental ballistic missiles (ICBMs) as the principal component of its force. The Americans, for their part, have generally relied on a technological lead in weapons development. The apples-and-oranges problem has been sidestepped in earlier strategic-arms pacts. But it has become a central question in the current talks.
For the Americans, a key incentive to talk arms control is unprecedented popular pressure in the West to curb nuclear weaponry. Also, the Reagan administration is determined to try to negotiate away what it terms the ''first-strike'' threat of the Soviets' ICBM force and, in Europe, of medium-range Soviet SS-20 rockets targeted at Western countries.
The first threat is disputed by some Western arms analysts - who argue that the US has enough retaliatory credibility in less vulnerable submarine and airborne forces to deter any preemptive strike against its aging land-based missile force. The second alleged threat is more generally accepted by Western analysts.
For the Soviets - who are immune to popular ''antinuke'' pressure, much less to the possibility their rubber-stamp parliament will tamper with funds for new military programs - the main incentive lies in concern about US plans to deploy a new array of strategic weaponry for which the Kremlin has no credible, early answer.
Two US systems in particular - the land-based MX missile and submarine-launched Trident - could afford the Americans the very first-strike option now attributed to Moscow. A third system, the slow but radar-elusive cruise missile, is virtually immune to the kind of air defense the Soviets currently deploy. The Soviets, further, want to head off deployment of some 600 new US missiles in Western Europe - most of them cruise missiles.
But there are also disincentives to compromise:
The US may prove reluctant to rush into a strategic-arms accord that limits these new weapons unless it includes an ICBM cutback of proportions Moscow so far seems unwilling to make.
The Soviets aren't about to negotiate away a good chunk of their ICBMs - even to limit new US weapons, in a trade merely hinted at so far by US officials - if it appears that grass-roots or parliamentary pressure in the West may force a cap on the West's arsenal anyway.
The same goes for the Soviets' medium-range SS-20 missiles - each training three highly accurate warheads on West European targets.
A foreign ambassador in Moscow remarks: ''There is a perception among many following the arms-control process that treaties depend on good will, or trust. Arms accords between the superpowers have historically depended, and continue to depend, principally on something quite less romantic: each party's assessments of its own interests.''
For the Soviets, those interests are pretty much the same under new party leader Andropov as under his predecessor.
They consist, first, in preserving nuclear parity with the US won through years of hard work. This priority is a given. The West should believe Soviet leaders when they say the Kremlin is determined to find a credible reply for any new Western system not subject to negotiation.
At the same time, the Kremlin would like to bargain its way into a much more manageable arms race - one that spares unnecessary strain on an already strained domestic economy and minimizes the abiding US technological advantage in weapons development.
The Americans' interests are harder to pigeonhole. ''Bourgeois democracies,'' as Moscow propagandists term governments of the US type, are sloppier than workers' states. Not all people vote for the same candidate; and they demonstrate for causes that are not officially sanctioned.
As a Soviet official remarked frankly in an interview on the eve of the first strategic-arms talks with the Reagan administration, ''These talks will give [ the administration] an opportunity for greater realism. . . . I think in the United States, a democratic country, not everything can be decided by the president.''
When President Reagan moved into the White House, his immediate concern was to ''rearm'' America to balance a Soviet buildup he argued had opened a ''window of vulnerability'' for the West. Talks on reducing nuclear arsenals were also on the agenda but, he suggested, lower down.
In the intervening two years, the two items seem to have moved more nearly into side-by-side slots, and officials increasingly hint that priority arms programs might be bargained away or curtailed as part of a negotiated accord with Moscow. The public emphasis on negotiation has grown further since Mr. Andropov became Soviet leader on Leonid Brezhnev's death in November.
Indeed, although neither side has made major concessions, both superpowers have in recent weeks toned down their rhetoric and spent much more of their public voice power on the substance of arms control.
The state of play remains unencouraging but is not without hope.
On the strategic arms front, the Reagan administration has presented a reduction blueprint whereby each side would cut back to roughly 5,000 warheads in a first stage - with an explicit sublimit on the land-based missiles traditionally central to the Soviet force. The proposal, at least in a first-stage accord, would not explicitly limit new US systems like the cruise missile, MX, or Trident.
The Soviets say this is unacceptable, and there is no reason to disbelieve them. Instead, Moscow has proposed an overall 25 percent cut in strategic launchers, with possible later provisions for warhead ceilings, while stipulating that each side must be allowed to decide how to make the trims.
In other words, the Soviets must not be made to restructure their strategic force to rely more heavily on submarine and airborne launchers, as the US already does. Particularly in submarine launchers, the US commands a technological lead.
At the same time the Soviets have sought a freeze on long-range cruise missiles and have suggested, generally, that both the cruise and systems like the land-based MX and submarine-launched Trident be limited in a first-stage accord.
On European nuclear forces, the US and its NATO allies want Moscow to scrap its more than 300 SS-20 missiles and other, older medium-range rockets, in return for shelving plans to begin deploying new US cruise and Pershing missiles in Western Europe by late this year.
Mr. Andropov has offered instead to remove all but 162 SS-20s from the European part of the Soviet Union - a figure equal to the total of current British and French nuclear missiles. The Soviets argue, correctly, that the West's tally of the European nuclear balance omits the British and French forces , as well as ''forward-based'' US warplanes capable of carrying nuclear weapons.
The West argues, correctly, that the British and French missiles are no match for the muscle power of the SS-20s and that, furthermore, the arsenals of London and Paris are neither under NATO command nor designed to protect fellow NATO states in case of an SS-20 launch; also, that Soviet tallies omit some Soviet aircraft analogous to the US ''forward-based'' bombers.
Western officials add that a commitment merely to move the easily mobile SS- 20 from the European part would not remove its threat to West Europe. For one thing, the missiles could still hit Western targets from the Asian USSR. For another, the SS-20s could be shifted back to European soil.
On an issue relating to both sets of talks - agreement on ''confidence'' measures to reduce the danger of accidental nuclear conflict - both sides appear to want progress. Measures like Mr. Reagan's proposed improvement of the Moscow-Washington ''hot line,'' in particular, present no problem for Moscow. But for now, the Soviets suggest their formal agreement on such steps is contingent on Washington's budging from its initial arms-negotiating positions.
Generally, senior Soviet officials say privately, there is room for compromise in both sets of Geneva talks, however. So do some US sources.
Among possibilities mentioned hypothetically is the partial scrapping of Soviet SS-20s in return for partial limiting of new US missile deployment.
On strategic weapons, the suggestion is that the Soviets might agree to some limit on their land-based ICBM force as part of a treaty also limiting new US weapons like the cruise missile, the MX, or the Trident.
More neatly packaged accords - like a leak-proof ''freeze'' on nuclear weaponry - meanwhile seem unlikely.
The ''freeze'' has for all practical purposes been rejected by the US administration, which argues that it would serve to formalize a Soviet nuclear advantage. And although Moscow has moved publicly to encourage overseas freeze advocates, the Soviets, too, seem suspicious of such instant arms curbs.
So far, at least, the Soviets' publicly detailed version of an acceptable freeze would allow at least some ''modernization'' of existing weapons systems. Moscow has not been explicit in defining what that would mean. In the past it has been quite elastic in its interpretation of the term. The replacement of far less potent medium-range missiles by the SS-20, for instance, is officially termed a ''modernization.''