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As the world watches the obliteration of the Syrian city of Homs and the crisis spills into neighboring Lebanon, it is time to ask what separates great powers from small powers. Turkey’s international star has risen steadily over the past few years, with Prime Minister Recep Tayyip Erdoğan being lionized in many Middle Eastern and North African countries, and Foreign Minister Ahmet Davutoğlu traveling the world as the representative of an increasingly influential power. Indeed, Turkey and Indonesia have joined the BRICs (Brazil, Russia, India, and China) on the list of the most important rising global players.

Now, in Syria’s carnage, Turkey is facing a critical test of its regional and global aspirations. It is time for its leaders to stop talking and start...