Military-strategy = Large scale planning. Think divisions and armies
Military-tactics = Small-unit planning. Man to man, platoons and such.
EDIT: Dictionary sez
strat·e·gy ( P )
n. pl. strat·e·gies
1.
1. The science and art of using all the forces of a nation to execute approved plans as effectively as possible during peace or war.
2. The science and art of military command as applied to the overall planning and conduct of large-scale combat operations.
2. A plan of action resulting from strategy or intended to accomplish a specific goal. See Synonyms at plan.
3. The art or skill of using stratagems in endeavors such as politics and business.
tac·tics ( P )
n.
1.
1. (used with a sing. verb) The military science that deals with securing objectives set by strategy, especially the technique of deploying and directing troops, ships, and aircraft in effective maneuvers against an enemy: Tactics is a required course at all military academies.
2. (used with a pl. verb) Maneuvers used against an enemy: Guerrilla tactics were employed during most of the war.
2. (used with a sing. or pl. verb) A procedure or set of maneuvers engaged in to achieve an end, an aim, or a goal.