Thanks for the reminder
I had forgotten that detail of the Puppeteers, one of my favorite SF alien species.
As I recall, they are not so much cowardly as extremely self-preserving... and their perceived tendency to turn their back on an imminent fight actually brings to bear their best weapon. The Puppeteers are tri-pedal, and their single hooved rear leg has a lethal kick, while they balance on their two forelegs and rotate their eyestalks to look behind them.
With Puppeteer irony, their leader is called the Hindmost (Devil take him!)
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[I know you recall all this, ER... I'm being instructive for those who've yet to savor Niven.]