According to satellite images captured by the commercial imagery and analysis firm ImageSat International, the Russian military has commenced a major modernization effort of its forces in their Baltic enclave of Kaliningrad. This news, coupled with previous revelations made during the summer about upgrades to what appear to be nuclear weapons storage sites, paint a troubling picture for NATO allies in the region.

Kaliningrad is a small Russian satellite territory sandwiched between Lithuania and Poland, with the Baltic Sea to its west. Although detached from the Russian mainland, its overland proximity to Russian ally Belarus makes it of particular strategic import. With Kaliningrad to the west and Belarus to the East, Poland and Lithuania share only a short border that stretches a bit further than 60 miles. This narrow territory, known as the Suwalki Gap, represents a lifeline for the Baltic nations to the north, which include Lithuania, Latvia and Estonia. If Russian forces from Kaliningrad and Belarus were to converge in the Suwalki Gap currently, there’s little NATO forces could do to keep the Baltic region from being severed from overland reinforcements and supply lines.

This modernization effort isn’t only some light housekeeping. Satellite images suggest the construction of more than forty new bunkers at a military storage area near Primorsk. To the north, upgrades to the Chkalovsk air base include the construction of a railroad and the installation of a new instrument landing system designed to aid pilots in landing during inclement weather. Most troubling, the Russian based called Chernyakhovsk that serves as the duty station for Russia’s the 152nd Missile Brigade has reportedly taken delivery of nuclear-capable Iskander missiles — which are short range, strategic ballistic missiles.

Another matter of concern for NATO forces in the region are suspicions of a Russian-developed digital denial system that some believe was tested during last year’s large-scale Zapad military drills. Baltic forces reported issues with cell phone coverage and radio communications intermittently throughout the drills, suggesting that Russian troops were experimenting with a system that may aim to sever communications within the region. That sort of digital blackout could mean disaster for NATO forces that would need to coordinate a response from around the continent if they hoped to counter a concerted Russian offensive.

Of course, the real deterrent stopping Russia from taking any aggressive action in Europe, one could contend, is finances, rather than fear of NATO retribution. Russia’s economy continues to struggle under the weight of U.S. led sanctions, and its military apparatus has been forced to pick and choose which programs to fund and which they’ll allow to collect dust amid their current financial woes.

That doesn’t offer the people of the Baltic states much comfort, of course, as Russia has clearly demonstrated that developing a powerful military presence in their backyard is among the initiatives the Kremlin feels is worthy of funding at the expense of other programs.