Complex sentence: The Brusilov offensive began on June 4 1916, it was the greatest Russian feat of arms during World War I, and among the most lethal battles in world history, and it was a major offensive against the armies of the Central Powers on the Eastern Front.
Split into simpler sentences: The Brusilov offensive began on June 4 1916, it was the greatest Russian feat of arms during World War I, and among the most lethal battles in world history. It was a major offensive against the armies of the Central Powers on the Eastern Front.