A deterrence, to make war too difficult to undertake.
Adding additional countries around the edge of NATO does two things for the countries currently in the pact, even if they aren't economic or military powerhouses. First, those countries are less likely to be attacked, and not having your neighbors be embroiled in war is good. Germany is much happier if there is no land war going on next door in Poland, bombs occasionally falling on the wrong side of the border, civilian refugees looking to them for safety.
Second, adding someone else to the pact puts someone else on the front lines to test the defense provided by the pact, if shit hits the fan. Sure, if Russia wanted to, they could try to bypass Poland on the way to Germany, but practically speaking with Poland in NATO, Germany will get to see how NATO responds to an invasion of Poland, rather than finding out how they respond to an invasion of Germany. Poland, likewise, would be much happier seeing how NATO responded to the invasion of Ukraine-the-NATO-member, rather than watching the invasion of Ukraine and wondering how NATO will respond to the invasion of Poland if Ukraine falls.
A defense pact, in case shit hits the fan.
A deterrence, to make war too difficult to undertake.
Adding additional countries around the edge of NATO does two things for the countries currently in the pact, even if they aren't economic or military powerhouses. First, those countries are less likely to be attacked, and not having your neighbors be embroiled in war is good. Germany is much happier if there is no land war going on next door in Poland, bombs occasionally falling on the wrong side of the border, civilian refugees looking to them for safety.
Second, adding someone else to the pact puts someone else on the front lines to test the defense provided by the pact, if shit hits the fan. Sure, if Russia wanted to, they could try to bypass Poland on the way to Germany, but practically speaking with Poland in NATO, Germany will get to see how NATO responds to an invasion of Poland, rather than finding out how they respond to an invasion of Germany. Poland, likewise, would be much happier seeing how NATO responded to the invasion of Ukraine-the-NATO-member, rather than watching the invasion of Ukraine and wondering how NATO will respond to the invasion of Poland if Ukraine falls.