What are tactics, and why are they described as "context-dependent"?

Question

Accepted Answer

Tactics are the specific means and activities used to carry out a strategy — and they change significantly depending on the situation and which side you're on.
If strategy is the intent, tactics are the implementation: the concrete activities performed to realize a strategic aim.
"Context-dependent" means there is no universal best tactic. The right move depends on:

the situation (the "terrain" you're operating in),
which side you're on — an attacker and a defender pursue opposite tactics even within the same scenario.

For example, in cyber security a defender's tactic might be network segmentation, while an attacker's tactic in the same network is lateral movement — same battlefield, opposite playbooks.
Tip: Because tactics are situational, you must analyze the situation first (who are the actors? allies vs. adversaries? how hostile is the environment?) before choosing one.
Go deeper:

MITRE ATT&CK — the live catalogue of real-world adversary tactics and techniques: concrete proof that the right move shifts with attacker, goal, and environment.