Throughout World War II, during the cold war, and ever since, Switzerland has remained steadfastly neutral as global powers have pushed and pulled at one another. But that doesn't mean the Swiss have no military. And, if you didn't know, one night last week their Army found itself involved in the very type of situation that the government in Bern has tried so hard to avoid all these years. Well, that may be a bit of an exaggeration. Let's just say 170 infantrymen toting assault rifles crossed the unmarked border with Liechtenstein after losing their wayin what up to that point had been a routine training exercise. They penetrated almost two miles into the latter's territory before realizing their mistake and returning. In a more volatile region that might have touched off a shooting war. But apparently no one in Liechtenstein noticed the "invasion." What's more, the Swiss weapons weren't loaded, and since tiny Liechtenstein has no self-defense forces, there was no danger of a firefight. Later, the two governments worked the matter out diplomatically, and it seems there will be no repercussions. Anyway, said a senior Liechtenstein official, "It's not like they stormed over here with attack helicopters or something."