Which parts of the Iliad may have been added after the main composition?

Based on scholarly analysis of the Iliad's structure, language, and style, the most probable candidate for a portion added after the main composition is the night expedition described in the 10th book, which recounts the capture of the Trojan spy Dolon.1

While the Iliad is widely recognized for its powerful artistic unity, it is an oral epic that evolved through a long-standing tradition of performance. Because oral poetry is inherently fluid, the text underwent periods of both distortion and stabilization before reaching its final form. Scholars have identified this specific book as a likely later addition based on its distinct structural and stylistic characteristics.123