War/international rivalry does have a significant effect but it is not on technical innovation itself as much as upon widespread deployment. As Mr. William Gibson put it "The future is already here, it is just not evenly distributed".
The first discoveries of "radar"(where radio engineers noticed that aeroplanes in flight could disrupt radio signals) were in the early 1920s and Britain had already developed RDF pre-war. The jet engine was already being trialled pre-war (Heinkel and Caproni were very interested as well as Messerschmidt, the Hortens and Frank Whittle) and the Germans had already developed nerve gases fairly accidentally out of pesticides research. Some specific areas of military technology like tanks and the bazooka are very closely linked to war, it is true, but they and derived technologies, if any, have had limited impact on civil society. And even if no wars broke out in Europe there would still have been international rivalries.
Personally I think it unlikely that Europe could have gone through the 20th century with no wars at all. In a best case scenario, I think we would be looking at a situation where there were no big wars but probably a few small ones which the rest of Europe managed not to get entangled in other than pressurising settlements and peace talks. An AH/Italy spat over Albania, a Bulgar/Greek border conflict, a post-KuK Hungary and Romania fighting over Transylvania or a Catalan or Basque war of independence, for instance. Possibly also some multinational military action such as an armed intervention to carve up the remaining Ottoman Empire or a forcible settlement of Sino- Japanese wars. Plus a couple of South American wars where new military technology could be trialled on a small scale.