Hi rockafeller, let's check the issue🧐

Please forward this request to the Support Team: https://vikingsweb-support.plarium.com/web/en/problems/

They will surely assist you🙏

recommendation followed, I forwarded my question to the Support Team.

Thank you

💪😎

What happened is that your opponents have a level 4 stronghold (or above) with a Tower of Odin (or their allies do) and they initiated a stronghold siege.

In a siege the game generates troops (Jotunn marches) which attack the stronghold and the clan initiating the siege (and an ally) can put troops into the stronghold to defend it.

Killing Jottun troops scores points in the three CvC categories that you specify.  The members of the clan which initiates a siege do not have to drop their shield in order to place troops into the stronghold.

Troops in the stronghold can be attacked so you had an opportunity to disrupt what your opponents were doing.  Take a look at your Clan Chat or Common Chat and you may see a message telling you that your opponents have initiated a siege.  In the absense of such messages it means your opponents scored their points while helping an ally defend their stronghold.

When you reconnoiter your opponents before a CvC it is worth noting whether they, and their ally, have a level 4 stronghold.

You might also give some priority to developing your own stronghold to level 4 and building a Tower of Odin.

John 2 said 

"Killing Jottun troops scores points in the three CvC categories that you specify."

Unless you ran your own sh siege and/or were otherwise attacked on a tile or town,stronghold siege does not score points in the killing warriors during an attack catagory,but i am assuming the op confused total kills with that catagory perhaps,as  john otherwise correctly stated a sh siege scores points in 3 catagories

the three catagories are 

killing enemy troops (total)

killing enemy troops in the sh

killing enemy troops during defence

What a stupid rule.  Has nothing to do with the genuine battle...