False Calm
From Transformers Wiki
The False Calm refers to a period of time during the Great War when it appeared that the Decepticons had accepted they couldn't win the war and were winding down their operations.
Fiction
Animated cartoon continuity
In reality, the False Calm was a failed last-ditch attempt by Megatron to conquer Cybertron by sending his troops to the planet at sublight speed to avoid detection. The AllSpark Almanac II