Windowed mode or full screen mode?
What is basically happening is that your PC does not have enough graphics processing speed to keep up with the main processing of the game. On my PC I added an inexpensive ($40 or $50 after rebate) graphics card to give things a boost (helps with web browsing too because of all the stupid extra stuff web sites throw at you nowadays). Now in full screen mode it is good, but in windowed mode it still jumps. So what I do is use two shortcuts: one runs the game in full screen mode that I use to watch the combat replay, the other runs the game in windowed mode that I use for orders (which I like because I can so quickly and easily switch between apps like AE, Tracker, etc). The parameters are otherwise the same except for adjusting the resolution so that in windowed mode it leaves the task bar across the bottom uncovered.
"C:\Matrix Games\WITP AE - PBM #1\Beta2\War in the Pacific Admiral Edition.exe" -altFont -dd_sw -archive -d -px1920 -py1080
"C:\Matrix Games\WITP AE - PBM #1\Beta2\War in the Pacific Admiral Edition.exe" -altFont -cpu4 -dd_sw -archive -wd -pxf1920 -pyf1018 -noFire