Russian forces near the Baltic Sea are getting their act together. This month, the Kremlin is practicing rushing troops across Eastern Europe into the Russian enclave of Kaliningrad in the event of a crisis. The exercise has involved lots of warplanes.

So far in September, Moscow’s warplanes have carried out around 100 training sorties near Kaliningrad, a tiny Russian territory between Lithuania and Poland that is geographically separate from the rest of Russia.

The exercise involves both Su-24 Fencer and Su-27 Flanker fighter jets, according to the Russian Ministry of Defense. Mi-24 Hind and Ka-27 Helix helicopters—used for ground attack and anti-submarine warfare respectively—are also taking part.

The Ministry of Defense stated in a Sept. 15 notice that the warplanes fired or dropped around 250 missiles, 50 bombs and 1,500 30-millimeter shells.

The war game around Kaliningrad is just the latest in what adds up to the busiest summer for military activity in the Baltic since the Cold War. Starting in March, Russian planes carried out mock attacks on Sweden, snooped on Swedish islands, flew through Finnish air space and chased a U.S. RC-135 Rivet Joint spy plane into Swedish territory.

Su-34 Fullback fighters—Russia’s most advanced operational fighter—also took part in training in Kaliningrad in July.

But more than just aircraft, Russia is practicing moving ground reinforcements into the enclave. In July, the Russian military rushed 200 soldiers from the 76th Guards Air Assault Division battalion into Kaliningrad in heavylift transport planes, flying over Estonian territory during the return trip.

To be clear, military maneuvers aren’t evidence of Russian provocation in the works. But watching where Russia’s airborne assault battalions go is a good barometer for where the Kremlin expects a crisis. They also serve as a subtle warning to NATO as U.S. and allied troops gather this month for the Rapid Trident exercises on the Polish-Ukrainian border.