Final answer:
The redrawing of boundaries after the Ottoman Empire's fall caused conflict due to the disregard for ethnic and religious ties and the creation of states with mixed populations. The interests of European powers in the region and the Ottoman decline due to military and overextension issues also contributed to post-imperial strife.
Step-by-step explanation:
The change in boundaries after the fall of the Ottoman Empire led to conflict largely due to the redistribution of lands without sufficient consideration for the ethnic, religious, and historical ties among the people living in these regions. Following the empire's dissolution at the end of World War I, European powers carved up the Ottoman territories according to their own interests, often ignoring the complex tapestry of local identities and allegiances. This lead to the creation of new nation-states with arbitrary borders that grouped together diverse populations with longstanding differences.
For example, in the Arab Revolt of 1916, Arab populations, led by the Sharif of Mecca, fought against the Ottomans with the support of the British, who promised an independent Arab state. Instead, the post-war treaties led to the establishment of new boundaries which did not align with the locals' expectations, generating resentment and future conflicts. Similarly, in the Balkans, the emerging independence of states like Serbia, Greece, and Bulgaria from Ottoman rule was complicated by the interests of European powers, such as Austria-Hungary and Russia, which escalated nationalistic sentiments, leading to the Balkan Wars and later the First World War.