Aver said:
Kristin did the same thing with with Western army. It's easy to keep army busy. It's harder to defeat it.
On the Western Front the terrain was different than it is in the Pontar valley. That terrain denied the Imperials their ability to maneuver and allowed Henselt and Demawend to defeat the Eastern Army by a process of sound tactical defence followed by speedy counter attacks after the defeat of the Central Army at Brenna. Whereas in the Western Front the Nordlings had to send support from the Central Front to finish off de Wett's force as the terrain (while suitable for guerrilla warfare) was not conductive to allow the Nordlings to win through such tactics alone. The Eastern Nordling Forces defeated the Eastern Nilfgaardian army without support from the Central or Western Front.
The terrain in the Pontar proved crucial 1. it denied the Nilfgaardians their ability to move their cavalry as effectively. 2. use of strategic points in that terrarin forced the Eastern army to detach seizable forces to deal with strongholds which could not be bypassed due to the mountains in the Pontar valley and 3. the terrain forced Ardal aep Dahy to deploy his forces over too great a distance - allowing the Nordlings to defeat him piece by piece as he retreated south and before his force was cut to bits at Aldersberg - him with it.
Aver said:
But it's their tactic and it works perfect. Infantry keep sieges and cavalry going deep into country. They have the best cavalry on the world and infantry is just burden (too slow to keep up with main army) for it anyway.
Blitzkrieg all the way.
Their tactic was to isolate strong points - not to besiege them unless absolute necessary (such as when investing an important strongpoint or city). Getting caught up in multiple and ineffective siege battle runs counter to the tactic of blitzkrieg - it slows down the whole advance and just destroys all momentum. Ardal aep Dahy's decision to besiege and burn every village and city he could take in Aedirn and the Pontar slowed his advance to a crawl and prevented him of completely his main objective - cross and debouch the Pontar and join Coehoorn and the Central Army Group for the main battle at Brenna.
Cavalry without infantry support (and viz versa) is suicide - many a battle and campaign has been lost by cavalry running off and not co-ordinating their movements or attacks with the infantry and the other troop types (countless battles of the medieval and early modern period attest to this). Nilfgaard might have the best cavalry in the world but a force that relies on a single arms component to win battles or has them so isolated that they have no other support is doomed to failure. Even if your infantry are rubbish - it is best to have them on the field supporting you and not 20 miles away besieging a useless strongpoint that can be easily bypassed.
Aver said:
In past they have beaten mainly because of wizards. Twice. Now there are no wizards in Northern Kingdoms.
Only on certain paths there are no mages. And I don't think all of them were either at Loc Munne or caught up in the following massacres. Surely a number must have survived...particularly those who aligned themselves with the Kings in the first place.