Ariane was designed from scratch (mostly), it's just that everyone involved first cut their teeth on military use. The previous Europa rocket had parts from IC

Ariane was designed from scratch (mostly), it's just that everyone involved first cut their teeth on military use. The previous Europa rocket had parts from ICBM. As for liquid-fueled ICBMs - Soviet Union invested much longer into liquid-fueled ICBMs, including very heavy ones, something that paid off in keeping their space sector in expertise.