戦術, 戦略, and 作戦: overlapping defense plans and a route-marking decision
Compare defensive plans, an explicitly long-term business strategy, and a decision to mark a route.
戦術: changed tactics and a discussed plan
戦術 (せんじゅつ) means tactics or strategy. 「監督は後半から戦術を大きく変えた。」 means “The coach changed the tactics significantly in the second half.” The coach's significant change begins in the second half.
「相手の守りを崩す戦術を皆で話し合った。」 means “We all discussed a strategy for breaking down the opponent's defense.” The group discussed breaking down the opponent's defense; success is unreported.
戦略: defensive planning and a long-term business condition
戦略 (せんりゃく) means strategy. 「相手の守備を崩す戦略を監督が考えた。」 means “The coach devised a strategy to break through the opponent's defense.” The defensive objective overlaps with the 戦術 example.
「長期的な戦略なしに事業を広げるのは危険だ。」 means “It is dangerous to expand a business without a long-term strategy.” Long-term is explicit in this business sentence, rather than a fixed duration for every 戦略.
作戦: a pregame approach and route marking
作戦 (さくせん) means strategy or operation. 「試合前に守りを固める作戦を決めた。」 means “Before the game, we chose a strategy of strengthening defense.” The strategy was chosen before the game; duration alone does not separate these three words.
「道に迷わないよう、目印を残す作戦にした。」 means “We decided to mark our route so we would not get lost.” The sentence reports a decision to mark the route, without saying the marks were already placed.
Does choosing a route-marking 作戦 establish that the marks have already been placed?
Show the answer and why
No. The decision is reported, but completed marking is not. Read the overlapping defense plans and the explicit long-term business condition within their own examples.