Brewer's: Wooden Wall
When the Greeks sent to Delphi to ask how they were to defend themselves against Xerxes, who had invaded their country, the evasive answer given was to this effect -
Pallas hath urged and Zeus, the sire of all,
Hath safety promised in a wooden wall;
Seed-time and harvest, weeping sires shall tell
How thousands fought at Salamis and fell.