The Greeks city states among themselves. In modern history, the last time I know of democracies fighting democracies was the American civil war. Democracies generally don’t fight each other.
Therefore the other city-states had to fight them.
There shouldn't be a doubt that the idea of democracy was alive and well in the Greek isles, though not all of them thought alike.
I've heard many here on FR say that they would be eager to take up arms if states like MA, NY, etc. continue on with their dictatorial ways. Here's to hoping it will never come to that but if it did would that be a sign that there was no democracy among us or would that be a sign that some were willing to fight for democratic principles?