Can defensive pieces stay in the harbor until the haven is attacked?

Do they automatically respond to an attack?

yes can stay in harbor, no do not auto respond, you need to recall your def for incoming raids.  You can see the raid coming in and usually unless they chart the raid you can call for help in time from your bh and definately get yours recalled in time too.

Can defensive pieces stay in the harbor until the haven is attacked?

Do they automatically respond to an attack?

If you hide all in the harbour, it is called "turtle up". A real good strategy in some situations.

Something I was taught when I when I first started.. When logging off for the night or anytime I would step away for a min. Harbor and spend. Meaning spending all your resources and harbor your troops. At the time auto hide and the bonus from upgrading the harbor past 23 wasn't available yet. Plus at the time it was the begining of the server so there were alot of active players in the center of the map.