Lyrian-Rivian Army

Lyria with Aedirn issued about 13 thousand soldiers, including 3 thousand of calvalry. In the early days of the invasion 1/5 of these forces was cut off in the forts and fortresses.

2nd Nilfgaard-Nordling War (novels)
Part of the remaining troops had been withdrawn to defend the wing against light cavalry and Scoia'tael. The remaining army, about 6 thousand. 1,200 soldiers knights, was beaten in Aldersberg. After the fall of Lyria queen Meve. The current state of the armed forces Lyria and Rivia may be determined at approx. 8 thousand. infantrymen who fought as a diversionary force during the last war with Nilfgaard. Army kingdom has the best crossbowmen in the north.

3rd Nilfgaard-Nordling War (The Witcher 3)
As we can (or rather can not) hear from Ambassador var Attre, there was no resistance in Lyria or Aedirn which could mean that they dont catch to mobilized or queen Meve use a tactic from previous war.