Complex sentence: Gough--whom Haig was then subject to a great deal of political pressure to sack-dined with Haig on evening of 15 March, no indication that he was crying out for reinforcements.
Split into simpler sentences: Gough--whom Haig had been subject to a great deal of political pressure to sack-dined with Haig on evening of 15 March. There is no indication that he was crying out for reinforcements.