While war itself is destructive and did exact a great cost to Europe (it arguably ended European colonialism as it made Europe unable to maintain presence in th

While war itself is destructive and did exact a great cost to Europe (it arguably ended European colonialism as it made Europe unable to maintain presence in their colonies), preparation in the case of war is arguably constructive and lead to innovations. The Internet for one started as a DARPA project (ARPANET). The Interstate Highway was made for troop transport. Military contracts kept some aerospace companies afloat (basically subsidizing them) and enabled innovation that otherwise wouldn't be possible.