Complex sentence: In January 1916, British agents reported there was a Turkish force of around 25,000 in the Sinai, which reinforced the British high command's belief that a Turkish attempt to attack the Suez Canal was imminent.
Split into simpler sentences: In January 1916, British agents reported there was a Turkish force of around 25,000 in the Sinai. Which reinforced the British high command belief that a Turkish attempt to attack the Suez Canal was imminent.