The Chilean army has for the first time accepted responsibility for human rights violations carried out during military rule by Gen Augusto Pinochet.
Gen Cheyre had already said the army would never abuse again
The admission is a reversal of the army's previous position, which held that abuses of 1973-1990 were excesses carried out by individual officers.
In a statement, army commander Gen Juan Emilio Cheyre said the decision was "difficult but irreversible".
President Ricardo Lagos called it a "historic step" towards national unity.
In his statement, published in the Chilean newspaper La Tercera, Gen Cheyre said the army accepted physical and moral responsibility for "punishable and morally unacceptable acts of the past".
Under Gen Pinochet's rule more than 30,000 Chilean leftists were tortured, assassinated or simply disappeared.
At least 3,000 are accepted to have died.
'No ethical justification'
Gen Cheyre rejected oft-repeated theories that the effect of the Cold War on Chilean domestic politics in some way excused the army's actions during the military rule.
Gen Pinochet took power in a 1973 coup, ousting the democratically-elected socialist President Salvador Allende.
With this step, the army consolidates its integration to today's democratic Chile.
Ricardo Lagos, Chilean President
Allende killed himself as Pinochet's troops closed in on the presidential palace.
"Was that political scenario an excuse for the human rights violations that occurred in Chile? My answer is one and clear: no," Gen Cheyre said.
Current Chilean President Ricardo Lagos, visiting Brazil, described his "satisfaction and pride" that the Chilean army had made it clear that human rights abuses "cannot have an ethical justification for anybody".
"With this step, the army consolidates its integration to today's democratic Chile," he added.
The army admission comes ahead of a government commission report, due next week, that is expected to expose torture as an instrument of military policy during Gen Pinochet's rule.
The report will include testimony from up to 30,000 political prisoners tortured by Chile's army and secret police.
Gen Pinochet faces a number of prosecutions for alleged human rights abuses in the Chilean courts but is yet to appear in court amid concerns over his health.