Complex sentence: In the end, on October 4,1821, Pharmakis surrendered on on the promise that his life would be spared; the promise was not kept by the Ottomans, and Pharmakis was ultimately decapitated in Istanbul.
Split into simpler sentences: In the end, on October 4,1821, Pharmakis surrendered on the promise that his life would be spared. The promise was not kept by the Ottomans, and Pharmakis was ultimately decapitated in Istanbul.