[quote=@NecroKnight]
[@EveryMemeAKing]

So far, I have been the only one - whom has stated and explained how my society managed to retain Old World Knowledge. Not only in using 21st Century tech, but also improving on it. And slowly developing more themselves.
[/quote]

It's worth pointing out that while perhaps on some level retaining knowledge on how computers work does not equate being able to use that technology. First and foremost, the technical means we possess today is an effect of globalism and international trade, with materials like natural rubber imported from South America being a stepping stone to the production of artificial rubber from oil, to be used in any variety of sealing applications in combustion engines, tires, fuel hoses, and any application where the flexibility to take movement and varying levels of stress and heat in a given system where more rigid lines like copper or iron would run up against a certain point and not being made for those applications sheer or break.

Computer technology too is built on the backs of materials mined largely in Africa, assembled by more computers in delicate work in an manufacturing system of decreasing size and increasing efficiency.

Every modern tool and amenity - no matter how mundane it seems - is built off an interlinked architecture of equally advanced tools, or tools built in part through global trade. This architecture itself incredibly vulnerable in a nuclear event that would not only damage local energy production but also local manufacturing capabilities. The rise in sea levels also included in this RP would do an additional number to whatever means is left by drowning the large industrial ports and rendering the commercial shipping dead. Immediately after, the ability to receive new fuel oil to run international shipping to obtain those far away resources in a commercially viable way is gone and what is left is on severe short supply.

Consider also that for the most part fuel refineries - particularly at least in the United States - is coastal infrastructure so that newly refined fuel can be put directly in oil freighters for distribution into the world market. Many of the key industrial ports for that purpose is gone.

Which comes back around to the before point: you may know how to build a tank, but you can not possibly run a tank. The energy needs to run a factory to build a tank or to begin manufacturing the necessary replacement parts to operate a pre-war tank is out of the hands of every nation. Access to diesel fuel - particularly in Europe - would be difficult or even impossible since all viable fuel reserves are in the north sea and any remaining oil drilling platforms are probably too flooded or at an unsafe level given current sea levels and how this would be an effect in way of storms, never mind the industrial apparatus that would manufacture the tooled parts for these drills would also have been destroyed in the nuclear fire. The materials for computer boards in the targeting and aiming systems in these old tanks would have suffered degradation over time from the elements, never mind that without a running engine the batteries on board a tank may not be able to sustain life any longer than they would without an engine running to keep the computers functional for the first week, EMPs aside.

An event as large scale as this would be setting society way back.