It is the business of a general to be quiet and thus ensure secrecy; upright and just, and thus maintain order.
In war, intelligence is critical. This means your enemy will use all means, fair and foul, to learn of your plans.
A secret shared is no longer a secret. Whilst some may be trusted, even the sharing may be overheard. The trusted person may also be captured and tortured for their knowledge. They may be blackmailed or bribed.
The more critical the knowledge, the fewer should know. It is hence often better to keep major plans to oneself.