Why managers need communication skills?

Any man who reads too much and uses his own brain too little, falls into a lazy habit of thinking..

As analyzed by Henry Mintzberg , managers need communication for the following  inter-related roles :

Interpersonal role
It is necessary to ensure effective operation of organization system and to maintain proper relationship within the organization and with outside clients and suppliers. If  interpersonal communication is effective, internal systems will run smoothly.

Informational role
If the internal information system is effective, System such as stock control, personnel financial systems and quality control networks will operate smoothly. Short-comings and problems will be quickly identified and a proper remedial action will be taken.
Reference to:Albert Einstein
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Reference to Book: Business Communication for the material posted. Writers: M.K Sehgal & Vandana Khetarpal. Published in year 2006.