Which state faced the greatest challenges due to external rivalries?

The state that faced the greatest challenges due to external rivalries was arguably Poland.

Poland, located in Central Europe, has historically been a battleground for many external powers due to its strategic location. It has faced significant challenges due to external rivalries, particularly from its neighbours Germany and Russia. These rivalries have shaped Poland's history and continue to influence its present.

Poland's geopolitical position between Germany and Russia has made it a target of aggression and territorial disputes. The partitions of Poland in the late 18th century by Prussia, Russia, and Austria are a prime example of this. The country was literally wiped off the map, only to re-emerge after World War I. However, the peace was short-lived as World War II saw Poland once again become a battleground, with the infamous invasion by Nazi Germany in 1939 and subsequent occupation by the Soviet Union.

The external rivalries have not only led to territorial losses but also to significant demographic changes. The Holocaust during World War II led to the extermination of three million Polish Jews. Post-war border changes and population transfers also resulted in significant shifts in Poland's ethnic composition.

Moreover, these rivalries have had a profound impact on Poland's political system. The country spent much of the 20th century under communist rule as a satellite state of the Soviet Union, due to the Yalta Conference agreement between the Allies. This has had long-lasting effects on Poland's political, economic, and social structures.

In conclusion, Poland's history is marked by the challenges it has faced due to external rivalries. Its strategic location has made it a target for aggression and territorial disputes, leading to significant territorial, demographic, and political changes. Despite these challenges, Poland has shown remarkable resilience and continues to navigate its complex geopolitical situation.