Donald Trump has expressed some radical thoughts about foreign policy — including that the United States, as a member of NATO, can choose whether or not to come to the aid of an ally under attack. To better understand how alarmingly wrong such thinking is, it's worth reading a new novel by a former high-ranking NATO official.

The book — called "War With Russia, 2017" — describes a terrifying series of events. NATO members become embroiled in squabbles over funding and how to deal with Russia, leaving inadequate forces in the Baltic region. Emboldened by the perceived weakness, Russian President Vladimir Putin launches a surprise attack, taking Latvia, Lithuania and Estonia in a matter of days.

By the time Western leaders find the resolve to fight back, they face entrenched Russian troops protected by sophisticated air defenses — and by Putin's pledge to respond to any attack with tactical nukes. Outright nuclear war becomes a distinct possibility.