4 ideas
Bhishma teaches that when a king or a society is in existential crisis, the ordinary rules of conduct give way to a separate code in which survival permits acts normally forbidden. The code is bounded: it holds only while the emergency lasts, and it must be abandoned once normal conditions return. That limit is what separates adaptive necessity from permanent corruption.
The state's coercive power (danda) exists because without enforcement society collapses into matsya-nyaya, the 'law of the fish', where the strong devour the weak. Punishment is therefore not the opposite of dharma but its precondition. A king who withholds force out of squeamishness fails the vulnerable most of all.
After winning the war, Yudhishthira is sickened by the slaughter of his kin and wants to abandon the throne for the forest. He is told that walking away is itself a failure of duty, because refusing power after causing its costs leaves the survivors ungoverned. The remorseful winner's task is to rule well, not to purify himself through withdrawal.
The text repeatedly insists that dharma is 'subtle' (sukshma). Right action depends on context, intention, and consequence and cannot be read off a fixed code. Following rules rigidly can itself produce adharma. Ethical judgment therefore needs discernment built through reflection and instruction, not mere compliance.