Attention is an abstract term used to describe the varying levels of management, both micro and macro, that are inherent in S:44. While not true "resources", attention is an important part of gameplay.
Spring: 1944 can be quite a large-scale game, with players forced to focus on multiple varying aspects in order to ensure their success, from the control of individual units or groups of individual units, to capturing and controlling objective/flag points, expanding logistics storage and ensuring frontline units are kept with ranges of logistics sources, to designing defensive lines of artillery, anti-aircraft and anti-tank forces, and co-ordinating combined arms attacks to defeat enemy forces.
Almost every unit in S:44 must be "managed" in this sort of way in order to maximize their potential and minimize their drawbacks, often by combining their focus with other supplimentary units. Players must utilize a combination of infantry, support vehicles, tanks and tank destroyers, long-range artillery, aircraft and aircraft defense in order to plug as many "tactical holes" as possible, all of which requires a base amount of attention in order to accomplish.
Thus, the amount of attention necessary for successful gameplay becomes an important factor.