LotR -- Book 5 - Chapter 03 - The Muster of Rohan

[davem]

More on the War-arrow:

The king split up a war-arrow, which he sent off in all directions, and by that token a number of men was collected in all haste. (Hakon the Good's Saga)

"-ör, f. 'war-arrow' (sent round as a to of war); skera upp -ör, to summon a district to arms." http://www.northvegr.org/zoega/h197.php

Hammond & Scull refer the Red Arrow back to Morris's 'House of the Wolfings', which Tolkien had read in 1914 - "the Wolfings are summoned to war against the Romans in part by a messenger who carries 'the token of the war-arrow ragged and burnt and bloody' "(Chapter 2).

Don't know if Tolkien was drawing directly on Morris work - or if he was, whether he was drawing on it consciously.

So, the War-arrow was a common 'signal'/summons in the Norse world, & it seems (in some cases at least) that it would be 'split up' & sent out to different places as a summons. Tolkien's example is painted red but Morris's has it covered in blood.