It is now more than a year and a half (20 months to be precise) since Soviet troops invaded Afghanistan and a year since the union movement in Poland won out over the old-style communist government and, under the label of Solidarity, became the most vital and influential political force in the state.
Add to the above the fact that the invasion of Afghanistan at Christmastime of 1979 was the last forward or aggressive venture which Moscow has launched in world affairs.
From that time on Moscow has been busy hanging on to what it has rather than reaching for more positions of strength and influence in the world.
There is little reason to doubt that Moscow would take advantage of any new opportunity to advance its influence and its military position. It is the nature of empires to keep on growing when they safely can. The story has been repeated so many times in history that we can take for granted a Soviet inclination to expansion.
But history also has written a rule which has never yet been broken. Empires have a lifespan of their own. They rise, and expand until they reach a maximum size. Then there is a phase of consolidation. The consolidation phase is of variable duration. It can last for osme four centuries as in the case of the Roman Empire, or barely a century as in the case of Britain's Victorian empire. But there always comes a time when internal political forces, often rising out of unresolved economic problems, so weaken the fabric of the empire that it comes apart.
Some empires are broken up from waging a too expansive war. Some fall apart from internal weakness. But every empire in history has sooner or later gone from the phase of consolidation to a final dissolution.
The Soviet empire is subject to the rules of history. It can no more escape those rules than could Caesar's or Napoleon's or Victoria's or Hitler's empire. We cannot measure accurately the present condition of the Soviet empire. Conceivably, it is capable of further expansion. More probably it is entering a phase comparable to the Roman Empire at the time of the Emperor Hadrian who recognized the limitations on Roman power and built literal walls around its frontiers. You can see the remains of those walls to this day. One lies across the narrow waist of the island of Great Britain. More is to be found over German mountains and forests from the Rhine to the Danube.
Hadrian's reign lasted from Ad 117 to 138. The walls he built along the frontiers he drew held the Roman world together and the barbarians on the outside for over 250 years. That stands as a world record for the survival of an empire. Nothing since of comparable size has lasted for as long as 250 years. Perhaps the Soviet empire can, but events seem to flow faster in these modern times. Napoleon's empire collapsed after a bare 25 years. Hitler's lasted for less than 10.
In thinking about how to contain the Soviet empire within its present frontiers the important thing is to avoid giving it opportunities and temptations for further expansion. The Western powers have a special problem right now. A collapse of the Khomeini regime in Iran could easily happen at any moment.
That event, if it comes (which seems probable now), would present possibilities for exploitation to Moscow. But it would also present risks. Any Soviet move into the debris of a Khomeini collapse would further alert the Muslim world to the dangers of Soviet expansion. Even that might not be enough to persuade India and Pakistan to concert their policies, but it would alarm both of them and might even produce a cooperative attitude toward Moscow.
It seems more probable that since Moscow avoided attempting to interfere in Iran when the Shah's regime collapsed it will for the same reasons of prudence keep out if and when Khomeini falls.
The United States still suffers from its overextension of commitments in Vietnam. The Soviet Union seems to have overreached itself in Afghanistan. How else explain the acquiescence to the wondrous events of the past year in Poland?
Some enthusiasts around the Reagan White House in Washington enjoy the thought that American "warnings" have put a protective arm around Poland. It's a happy thought for those who indulge in it. The probable reality is that Moscow watched what happened to the US in Vietnam and is belatedly reading the result of its own intervention in Afghanistan.
The chances are that the "miracle" of Poland is due to the realization in Moscow that its empire has reached its maximum limits and that to attempt to push farther, or even to use force against Poland, would mean an overcommitment which might even lead to a dissolution of the empire itself.