Officially the forces trained how to combat "illegal armed groups" (terrorists), but the real reason for the exercises was to threaten Poland and the Baltic states:
“Russia has officially stated that these are anti-terrorism exercises,” Lithuanian Defense Minister Juozas Olekas told AFP. “But the number of participants and amount of military equipment indicates that that this is not their agenda.”
Senior Estonian military official Lt. Col. Eero Rebo said: “The Kremlin claims that the exercise is about fighting terrorism, but based on the information we have on Zapad 2013, the exercise has an anti-West agenda.”
“If you look at the Baltic sea region, the strategic balance has been changing quite drastically in the last decade, and not in our favor,” Latvian Defense Minister Artis Pabriks said Friday.
“We are concerned because we see such large-scale exercises in context,” he added.
Russia had informed NATO that 22,500 troops would participate in the Zapad 2013 exercises, but according to Swedish intelligence sources the real number was much higher, about 70,000. No wonder that people in Poland and the Baltic states are - and should be - extremely concerned.
On this Belorussian video you can see a soldier aiming at an unarmed Swedish Gripen reconnaissance plane (at about 2 min):