ABC News president David Westin is stepping down at the end of the year after 13 years. The move comes after tough 12 months for Westin that included appointing new anchors on all ABC News programs and dealing with severe staff cuts. The personnel changes he oversaw included naming Diane Sawyer as the anchor of World News, George Stephanopoulos as her replacement on Good Morning America, CNN veteran Christiane Amanpour as host of This Week, transitioning Chris Cuomo from GMA to 20/20 and Bill Weir from GMA to Nightline to replace Martin Bashir. Here are the memos from Disney-ABC TV Group president Anne Sweeney and Westin.

Sweeney: For the past 13 years, David proved himself a tireless advocate for ABC News, effectively guiding the group through some of the most seismic industry, and divisional, changes imaginable  During that time, he helped reinvent our News organization, and positioned us for great success going forward.  While it will be sad to see David leave, his desire to pursue other professional endeavors is understandable, and commendable, and I know you’ll join me in wishing him nothing but the best.   I’ll be announcing a new leader for ABC News in the near future.

Westin: A month ago I told Bob Iger and Anne Sweeney that the time has come for me to step down as President of ABC News.  Leading you has been a great privilege and a solemn responsibility — a responsibility that I tried to fulfill for over thirteen years by doing what I believed was best for this important news organization.  I will root for your continued success long after I am gone.

I’ve always admired those few who know when it’s time to move on.  This is the right time for me.  Over the last nine months, we’ve put in place new anchors on all of our programs.  At the same time, we went through a very difficult transformation made necessary by changes in our business and its economics.  I am confident ABC News is better positioned for the future than it has been at any time since I came here in March of 1997.

As rewarding as I’ve found my time here, there are some other things I want to do professionally — things that I cannot explore while fulfilling my responsibilities here.  I’m announcing my decision now so that I can pursue those possibilities, something I couldn’t do in fairness to all of you until I’d told you of my plans to step down.  I have agreed to remain your leader through the end of the year to ensure that Anne has the time she needs to find the right successor and that there is an orderly transition.  So, I’m not going anywhere for the time being.  I will need your support during this interim period to make sure that we continue to move forward.

I have only the highest regard for the company of which we are a part, for its leadership, and – most important – for all of you.  I am grateful for your letting me be part of this great organization for so long.