Centuries of Soviet and tsarist oppression taught the three Baltic states to bar their doors whenever the Kremlin issues marching orders. Now they also scramble Nato jets.
President Vladimir Putin's decision to hold snap military drills in the Baltic Sea last week, just as he was pouring troops into Ukraine's Crimean Peninsula, sent shockwaves through Latvia, Estonia and Lithuania.
The three republics demanded, and got, military support from Nato. The US deployed six warplanes to Lithuania on Thursday to bolster defences in the Baltic states for the first time since they joined the alliance in 2004, expanding the squadron to 10.
Another dozen will arrive in Poland on Monday, the country's Defence Ministry said.
About 150,000 soldiers took part in Putin's drills, including 3,500 from the Baltic Fleet in Kaliningrad, Russia's exclave between Poland and Lithuania.
"Russia today is dangerous," Lithuanian President Dalia Grybauskaite said at an emergency meeting of European Union leaders in Brussels.
"After Ukraine will be Moldova, and after Moldova will be different countries. They are trying to rewrite the borders after the second world war in Europe."
Fear over Russian expansionism is spreading across the former Soviet Union. Moldova, which borders Ukraine and Romania, has its own secessionist region, Transnistria, where Russian troops are stationed.
The former Soviet state is very "anxious" about Putin's brinkmanship, Prime Minister Iurie Leanca said in New York. Leanca said he called on President Barack Obama to provide "strong US leadership" to contain Putin.
The fear is particularly acute in Lithuania, the first republic to declare independence from the Soviet Union, in 1990.
Putin, who called the Soviet break-up the following year the "greatest geopolitical catastrophe of the century", accused Lithuania and Poland of training the "extremists" who ousted Kremlin-backed Ukrainian President Viktor Yanukovych in an "unconstitutional" coup.
Those "groundless insinuations" are attempts "to justify aggression and to incite hatred against Lithuanians", Foreign Minister Linas Linkevicius said.
A senior US military official said the Pentagon wasn't planning additional moves for now beyond the deployments of F-16 fighter jets to Poland and F-15s to Lithuania. Further actions to signal US resolve would be taken only if Russia adds to tensions in Crimea, the official added.
The Pentagon's intent is that the Nato alliance emerges stronger from the crisis than when it started, and military planners are seeking a strategy that balances restraint with a show of strength, according to the official.
That means the US won't deploy aircraft or vessels close to Crimea, or add any hi-tech weapons systems such as F-22 stealth fighters.
The US Navy's guided missile destroyer USS Truxtun was scheduled to enter the Black Sea yesterday for previously planned exercises and a port call in Romania, the navy said.
Like Ukraine, the Baltics, home to more than six million people, have a large Russian minority.
About a quarter of the population in Latvia and Estonia consider themselves Russian. In Lithuania, the figure is about 6 per cent.
"The Crimea scenario resembles the occupation of the Baltic states by the USSR in 1940," Latvian Foreign Minister Edgards Rinkevics said. "History repeats itself, first as tragedy, second as farce."