In the last 20 years, we learned a lot about how Communist societies come unglued. There were various scenarios, various results. East and West Germany unite, the Czechs and Slovaks split, Poland proves adroit at adapting to both democracy and capitalism, Ukraine fumbles both.

But a key factor in all the scenarios is whether at the critical moment the powers-that-be used force to retain power. These could be called the Tiananmen Square and White House moments. The Chinese used force, the Soviets did not.

In this decade, Cuba will almost certainly face that critical moment as well. Cuban is unique in having a large exile community located close by that will want to actively shape the country’s post-Communist future. Some exiles want the return of property that was confiscated or abandoned. Their political conservatism may not sit well with those Cubans wishing to preserve the achievements of the revolution. The Cuban exile community could in turn involve the United States, especially since in another unique development the United States already has a military base on Cuba.

Russia views Cuba as a counterweight to possible NATO membership for Ukraine and to U.S. missile emplacements in Europe. Moscow wants a stable Cuba, one hostile to Washington. Nikolai Makarov, chief of the General Staff, visited Cuba last year to see about beefing up Cuba’s air defense.  

Cuba could easily get caught up in the missile game that the United States and Russia have been playing since 2008 when President George W. Bush planned to counter Iranian missiles by placing interceptors in Poland. President Dmitry Medvedev responded by threatening to place missiles in Kaliningrad. U.S. President Barack Obama withdrew from the Bush plan, temporarily improving relations with Russia.

But Obama has upheld the U.S. promise to provide Poland with Patriot missiles. Those missiles will be installed 100 kilometers from Kaliningrad. The Russians aren’t protesting this because of their current rapprochement with NATO, after the break caused by the 2008 Russia-Georgia war. The Russians want NATO combating Russia’s enemies in Afghanistan — mainly radical Islamists and drug traffickers — and for the moment Ukraine is leaning away toward the Kremlin.

But that could all change in a few years. Ukraine’s new pro-Moscow leader may fail to deliver the goods, causing Kiev to look westward again, at which point NATO’s work in Afghanistan should be coming to an end. Then NATO, no longer needing Russia’s cooperation, might be tempted to resume recruiting Ukraine. Cuba would then become of great significance to Moscow.

Moscow will not supply Cuba with offensive missiles, but it could build up its defensive capabilities in a way that would be destabilizing. The United States and Israel, for example, are adamantly against the delivery of S-300 missiles to Iran because they provide an effective defense against aircraft and missiles, both cruise and ballistic.

Cuba could get those S-300s directly from Russia — how could Washington protest when Poland has Patriot missiles? — or from Venezuela which ordered some in 2007 and will take delivery this year or next. The Venezuelan military is already so infiltrated at the highest levels by the Cubans that the Venezuelan vice president/defense minister resigned in protest in late January.

All this gives the Russians a strong card to play, but it could be a risky one if it is played while Cuba is coming unglued. The United States better have something equally as good in its own hand — or up its sleeve.

Richard Lourie is author of “The Autobiography of Joseph Stalin” and “Sakharov: A Biography.”