In English, the expression, "in the first place", is used (not exclusively but) when things have gone wrong and it's clear that something should have been done differently, at the incipient stage of the process--"in the first place".
In CHAT cmw set the following translation-teaser:
"What would have been wise is that Putin should never have invaded at all!"
After the initial wave of panic subsided, I realised that it was a conditional sentence:
"prudens fuisset, si Putin non invasisset primum."
"It would have been wise if Putin had not invaded in the first place."
Cerberus indicated that, in Latin, adverb, "primum" & adjective-as-substantive, "in primo", do not mean "in the first place" as explained above. This, exemplifying the care that must be exercised with dictionary definitions (Oxford). Studies of Lewis & Short ("primus") and Allen & Greenough section 322(d), p.198 give these as being parts (first) of an ordering. A & G:
"Primum means 'first' and implies a series of events or acts. Primo means 'at first', as opposed to 'afterwards', giving prominence merely to the difference of time."
Note: "In enumerations, 'primum' (or 'primo') is often followed by 'deinde', 'secondly', 'in the next place', or by 'tum', 'then', or by both in succession.
A & G provide examples but the best is from L & S:
"...primum averti pecuniam domum non placere, deinde..." =
"...first of all (in the first place) that he must not take to his own house the money given for those purposes; secondly..." (Cic. Ver. 2.2.143).
(L & S also offer "primum"-plus-"denique".)
Returning to the original teaser: Putin would have to have done/ be about to do more-than-one thing in order to justify, "primum" (-plus-"deinde").
Cerberus suggested the use of, "denique" = "in a word", "indeed"; or, "omnino" = "at all". The last giving: "....had not invaded at all.", which is a good fit.
Concluding: is there a way to say, "in the first place", in this sentence or is Cerberus's alternative the best (only) way to go?