If not true, how long ago was the last one?
At the risk of brushing up against the 20 year rule (though it just barely makes it), I'd strongly challenge the contention that we're in a period of 70 year long Europe-wide peace. The Yugoslav wars of the 1990s were massively violent conflicts, containing such atrocities as the massacre of over 8,000 civilians at Srebrenica in 1995 (see? Not a 20 year violation...by one year).
The Yugoslav wars aren't even the only ones to consider...the Soviet invasions of Hungary in 1956 and Czechoslovakia in 1968 could both qualify as wars.