Short answers, pulled from the story.
The word strategy emerged in the 18th century as a narrow concept known as the art of the general. Before this period, military thinkers viewed war through three distinct arts or sciences: tactics, logistics, and strategy itself.
Sun Tzu outlined thirteen principles in his famous treatise The Art of War. These principles influenced Chinese, Japanese, Korean and Vietnamese historical tactics for over two millennia and focused heavily on asymmetric warfare and deception rather than direct confrontation.
Johann von Bourscheid translated Leo VI's Tactica into German as Strategie in 1777. This translation spread the word throughout Western nations and marked the beginning of serious study of military strategy in Europe during that era.
Soviet strategy during the Cold War aimed to prevent invasion of Russian soil at all costs. The USSR adopted a nominal no first use policy that functioned as launch on warning posture while NATO divided its strategic policies into distinct periods from the 1950s through the 1980s.
Technological change affected leadership less than it transformed operational capabilities during both conflicts. Germany used radios in every tank as a key enabler for mobile warfare yet officer control over troops declined despite increases in army size.