There is a particular coldness to a World War II map key. It sits in the corner of the sheet like a ledger of grief, a small block of ink that turns a sheet of paper into a record of slaughter. You look at the hatching, the arrows, the dotted lines, and you realise that every symbol was somebody's son, somebody's street, somebody's last morning. The key is not decoration. It is a confession, written in the plainest language the cartographers could manage, because anything more would have been unbearable. In Ireland, poring over such maps during the Emergency, people read them with a strange, guilty distance — neutral, safe, and still able to trace the exact line where Europe was being torn apart.
Read a wartime key closely and it becomes a dictionary of ruin. A thick red band means ground held by the Axis; a blue line means the Allies; a black smear