-Written by David Whittier

Anyone who has taken any ICS training or been involved in any sort of emergency management exercise has been exposed to the concept of Command.  On the surface, the idea seems straightforward.  Dictionary.com defines command as “to give an authoritative order”.  So, I command you to do something, then you do it.  Simple, right?

Not so fast.  ICS methodology speaks about Command in three different contexts: Chain of Command, Unity of Command, and Unified Command.  So, what does Command mean then, when you are working in an Incident Command Post?  And how do those three terms relate to each other?

The first two are relatively simple, so we’ll deal with them first:

Chain of Command: everybody knows who their boss is.

Unity of Command: everybody has one boss.

Which leaves us with Unified Command.  What does that mean, and why can’t we just use the idea of Unity of Command?  One person in charge at the Incident Command Post (ICP), and everyone follows her direction?

The reason is that sometimes you will be faced with an incident that spans more than one agency or more than one jurisdiction, either functionally, legally, or geographically.  For example, Fire and Police.  When that happens, you will find the senior person from these jurisdictions will attend the ICP, rightfully expecting to exercise command over their own people.  How do we manage this?

ICS uses the idea of Unified Command to enable agencies with different legal, geographic, and functional authorities to work to share incident management and function in a coordinated manner.  The key here is for those authorities to develop a common set of incident objectives and strategies and issue a single Incident Action Plan.  This allows functional authorities to make joint decisions and speak with one voice.  Within the jurisdictions, Unity of Command still applies, so that the police lead is not telling the firefighters how to do their job.

This method works well in practice, although there is often the idea of “first amongst equals”.  For example, in an incident where Fire is fighting an apartment fire and Police are providing traffic control, the objectives related to dealing with the fire will take precedence over the objectives dealing with the traffic control.  The key is that decisions are made jointly and communicated with one voice from the ICP, not that one agency issues all of the directions for the incident.FEMA has a good video on the topic: https://www.youtube.com/watch?v=gvCNAVw_oPg. It is about 25 minutes long but is worth the time.