Russia's willingness to attack Ukraine (and Georgia before that) makes new NATO states wonder if Putin would attack a NATO state if the opportunity arose. So the Baltic states want tripwires:
The Baltic states will formally ask NATO to deploy several thousand troops as a deterrent to Russia, Lithuania said Thursday, but the alliance gave no assurance that the request would be accepted. ...
"We are seeking a brigade-size unit so that every Baltic nation would have a battalion," military spokesman Lithuanian Captain Mindaugas Neimontas told AFP.
Were I God of the NATO wish response department, I guess I'd put a British reconnaissance regiment (battalion) in Estonia so it could screen the border and fall back; a US Marine battalion in Riga, Latvia, where it would guard the equipment of a full brigade to provide a rally point for units retreating from Estonia and the Latvian border (and possible hold on the flank if the Russians keep driving south; and a French or German tank battalion in Lithuania, to prepare for the counter-attack north.
I'd have brigade sets for American, German, and British heavy armor units in Poland, too. If I was asked.