[@Buddha] to quote:
'Perhaps Eskanadra had a good enough relationship with Dieuporteille...that they answered a call to arms against the heathen hordes. Thoughts?'

Basically, when the hordes invaded, Andaluja did not yet exist. What say you that Dieuporteille called upon the Eskanadrans in the war to subjugate the horde? (Eskanadra had a good quality, large military before they joined the Grand Kingdom, but the King forced them to dismantle it once they joined).

So:
Dieuporteille halt the Horde
Grand Kingdom mobilises to subjugate it
Dieuporteille call upon Eskanadra to help defeat the heathens
Combined forces subjugate the Horde