This message is a conspiracy consistent with recurring pro-Kremlin narratives about the West's attempts to stage a colour revolution in Belarus, to turn Belarus into an anti-Russian country, and about Poland's plans to partition Belarus and establish the Fourth Republic.
The message refers to alleged Polish maps in use during 2018 military exercises. ANAKONDA 2018 was a Polish-led multinational military exercise which took place in November 2018. It involved around 12,500 troops in Poland and approximately 5,000 troops from 10 NATO allies in the Baltic states and aimed to increase interoperability between the allies.
During the exercise, a number of webpages with dubious reputations and unknown ownership including Opednews.com published an article allegedly presenting NATO military scenarios. The article contained four maps, allegedly of the Polish military. On one, Western Belarus was shown as being taken by US, Polish, Lithuanian, and Latvian troops.
This article in Lithuanian, alleging aggressive NATO plans, was briefly published by Lithuanian internet portal Kas vyksta Kaune without editorial authorisation, as a result of a cyber-attack. The publication of this propaganda about NATO's planned invasion to Belarus due to a cyber-attack against a Lithuanian internet portal was widely covered in the Lithuanian press (see here and here).