What are the effects of war on a country's political development?
There is no one way to answer this question. If we look at history, wars do different things for each country. In light of this, the best we can do is to give examples of what may happen.
If you look at the Korean War, the political development in the aftermath of each country was radically different. North Korea became communistic and South Korea embraced a democratic form of government. This is a dramatic example, because one country went in two different ways. And when we look at the two Koreas the differences could not be starker.
If we turn out gaze else and examine the ancient world, the Persian War with the Greeks made the Athenians an imperial power, because the Athenians worried that the Persians would strike again. For them, it was only a matter of time. So, they created the Delian League. In time, the treasury of the league was moved to Athens, and Athens really did become an imperial power. So, the Persians Wars made Athens more imperialistic, as other cities paid tribute.
These two examples show what could happen. The point is that we need to look at war and political development on a case by case basis. There is no one size fits all.