This is one of the most important and controversial decisions taken by Amnesty International throughout its history. In 2005 the International Council Meeting of AI took a decision that gives the right to the organization to support military interventions in order to "prevent or end imminent or on-going widespread and grave abuses of international human rights or humanitarian law". Considering the international bodies deciding and executing military interventions (UN Security Council, NATO, etc.) this AI decision seems to be in favor of the great political and military powers of the world. It´s hard to imagine an international military intervention without grave human rights violations (think of Yougoslavia, Afghanistan, Iraq, Libya etc.). After all it´s not the job of a human rights organization to support military interventions but to monitor and condemn human rights violations.
You can read the whole internal document of AI guidelines on this issue here.
Here is the first part of the introduction, with the main position of AI on military interventions:
"The 2005 International Council Meeting (ICM) adopted a wide-ranging resolution on the
protection of human rights through conflict prevention, intervention and condemnation of
the use of force. In the resolution, AI recognises that peaceful resolution of conflicts is a
prerequisite for the realization of human rights, and that armed conflicts inevitably produce
human rights violations. The resolution outlines a wide range of steps that AI can take to
strengthen its work on conflict-prevention and conflict-resolution. The resolution then states
a new AI policy on the use of military force as follows:
Amnesty International is an independent and impartial human rights organization that
generally takes no position on the desirability or otherwise of particular military
interventions or other forms of armed conflict, other than to demand that all participants
must respect international human rights and humanitarian law;
In exceptional circumstances, taking full account of its country strategies, commitment to
women’s human rights, and other relevant considerations, Amnesty International may:
• oppose the use or threat of use of military intervention that is particularly likely to
lead to an increase in human rights abuses;
• call for or endorse ceasefires or urge the parties to a conflict to negotiate;
• call for the use of armed force (including military or law-enforcement forces) to
alleviate, prevent or end imminent or on-going widespread and grave abuses of
international human rights or humanitarian law (such as genocide, crimes against
humanity, and war crimes), or the actual threat of such a situation, provided that:
(a) the force is in conformity with international law;
(b) the force is given a mandate to use proportionate force, as necessary, to protect
(c) such calls will be limited to the deployment or strengthening of UN peacekeeping
or similar operations.
 See Decision 2 of the 2005 ICM."