Possible acceleration systems

[The Architect]

relevant posts on the ToughSF blog. One of the biggest single factors may be the amount of kinetic energy wrapped up in the ships and how that can be used (or have to be defended against) in combat. Put another way - one of the most effective weapons in this kind of fight could be throwing a bag of gravel (or even just a bunch of glitter or a lightsail) overboard and slowing it enough so that your opponent then runs into it at high speed with an effect like a bunch of high explosives going off in their face.

Coming back to this, I think I've found the relevant article
http://toughsf.blogspot.com/2016/10/the-...ombat.html
One thing I notice here is that long range space combat is considered 10,000 km. This may be why there is very little about interstellar STL combat. I assume that at relativistic speeds you see and get seen a very long time before you can get anywhere near combat range. In this case, dodging techniques like using decoys would probably be deemed preferable. Combat would be the last resort when the starship is already failing at dodging and getting to that point may require a very large number of pursuers or sheer luck or a combination of both. Which is of course what is going to happen.
And then we would fall into that long range combat situation. The starship would have the superiority in weapons but the pursuers would have a superiority in numbers. The enemy would use some clarketech that allows them to split at will to multiply the targets and perhaps even recombine. And there would be a point where the starship is overwhelmed, at which point a new player shows up and basically saves the day. The new player would attempt communication, but the starship would just shoot it down according to standard procedure. Although not before it ejects a stealth microscopic module that will land in the starship's deceleration field (another clarketech that absorbs the kinetic energy of anything below a certain size (say a 100 microns?) that might hit the hull either straight at the front or at sideways angles relative to the direction of flight and is small enough to have escaped detection/deflection/destruction), manage to survive on or even inside the starship's hull and lay low.