Okay, so my world is basically classified into 9 quadrants, with 8 being land and the other being a single gigantic body of water. All of these land quadrants are separated from each other by water. But there has been a constant despise and a cold war going on between the quadrant 4 (Q4) and Q6, which are separated by about 10,000 km of water, for the last two centuries.
I want to know what could be an extremely complex reason for the war to prolong for so long?
It is not set in the 21st century or anything, but the technology is almost on par or may be slightly advanced than now and things like aeroplanes and computer technology have been present since the last two centuries.
The war is not because of reasons like resources such as land or money-related goods or power, but rather because of some complicated misunderstanding that happened centuries ago, in which both parties are correct in their own stand.
Both the quadrants are almost equally advanced and developed.
Remember, the cause is supposed to be highly convoluted (something that hasn't happened in our history ever) as both the quadrants are right in their prospective since it has been the cause of war for over 2 centuries.
Edited for further details:
In reference to query in the comments,
1) The cause for war is quite complex since there are only a handful of experts on either parties who can actually understand the essence of the cause in depth and it is quite difficult for the general population to comprehend it. This is one of the reasons for the war prolonging for so long.
2) The technology hasn't stagnated for two centuries. I mentioned that it may be considered to be slightly more advanced than present era's. This is in reference to the fact that how in the real world, technology was almost stagnant for millenniums together, but suddenly all the modern things that were invented which we use now, happened only in the last two centuries.