VILNIUS, Lithuania -- As he sat in his restaurant in the Lithuanian capital, Liutauras Ceprackas, a chef, said he was one of the many Lithuanians who worry about a Russian invasion. He is not sure, he said, that his country’s 15,000-soldier army is big enough to stop one. Increasingly, he is not certain an American-led NATO would, either.That is why, three generations after Nazi Germany brutally occupied his country in World War II, Ceprackas, 51, is glad that Berlin has permanently stationed thousands of German soldiers in Lithuania.“If they kill just one German,” Ceprackas said, referring to the Russian army,...