What's a realistic sample size for a B2B survey in defence procurement?

Honestly, with a population that small, even 30-50 completed responses would give you something statistically useful, but getting there will be brutal — response rates in defence procurement tend to be 5-15% at best. I'd actually do both: a handful of depth interviews first to build credibility and shape your survey questions, then push the survey to whoever's left. Trying to cold-survey that audience without warm relationships first is usually a dead end.