iran. cnn s ryan brown with more. reporter: good morning, michelle and dave. this most senior shakeup at the pentagon amid increased tensions with iran, acting secretary of defense pat shanahan stepping down, announcing that he will resign effective sunday we re being told. and this shakeup comes as president trump has said he is seeking to avoid war with iran while the u.s. simultaneously is deploying thousands of additional troops to the region to do forced protection, to say to respond to what it says is an increased iranian threat. 1,000 troops being ordered most recently. those forces will include reconnaissance personnel, missile defense crews. forces said to be defensive in nature but iran saying it will be prepared to respond if need be. the senior shakeup at the