I’m currently creating a Warforged character for a one-shot, so I need to decide who he/she/it fought for in the Last War (Warforged were created as weapons, so each of them must have fought for or at least been owned by someone). However, the lore is not entirely clear on the matter of who employed Warforged, as far as I can tell.
The sourcebook Eberron: Rising from the Last War states on page 12, under the “Dragonmarked Power” heading (emphasis mine):
The dragonmarked houses remained neutral in the war and made considerable profit selling their services to all sides. War drives innovation; House Cannith developed many new weapons during the war, including the warforged.
This seems to strongly imply that Warforged fought on all sides. As far as I can tell, however, it’s never explicitly stated.
Is there any explicit lore, whether in E:RftLW, WGtE or previous editions, that supports that assumption that the Warforged were employed by all nations?