[Taqwus]

Colonizing elsewhere and overall just boosting your score may also make them more likely to surrender.

With high tech cost and only 24 turns in, you don't have fighters, do you? Fighters are immune to missiles, so that would help with one problem...

On maximum range, you may want to try a 'tweaked' maximum range (identical to original, but with the secondary strategy of Don't Get Hurt). But simulate the battle before you commit...

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-- The thing that goes bump in the night