Navigation when wartime lights go dark

How were navigational aids maintained during wartime?

Normal service was often interrupted: lights were dimmed and Trinity House recovered or sank buoys, leaving crews more dependent on dead reckoning and maps.

Lights and other navigation aids could also guide an enemy toward a coast or harbor. Wartime authorities therefore dimmed lights and interrupted normal service, leaving mariners more dependent on dead reckoning and maps. Trinity House is described as recovering or sinking buoys so hostile ships could not use them to navigate into and out of British waters. The discussion leaves the additional navigation systems unspecified.