The Division Officer's Guide, Twelfth Edition, is a handbook for Junior Officers and Petty Officers of the U.S. Navy and U.S. Coast Guard afloat, in the air, under the sea and ashore. Originally written in 1952 by CAPT John V. Noel Jr., and last revised in 2004, the book provides division officers with basic lessons of leadership, organization, administration, training, and discipline - essential elements for success in their key positions. It offers much useful information on individual readiness, the conduct of assessments and inspections, maintenance processes and responsibilities, and the preparation and methods of correspondence and officer and enlisted career planning. The lessons and themes are not limited to use in the sea services; they provide a foundation for success in both military and personal life. Learning and practicing division officer skills lays a foundation for future success, no matter the environment or occupation, including the highest levels of the military, government, and citizenship. This twelfth edition continues to evolve with our rapidly changing world. Terrorism has become an international security issue, men and women now serve alongside superbly in all of our ships at sea, and technology continues to change virtually every aspect of naval operations. Cyber tools such as web-based information, use of computer networks aboard ships, and the ability to post and share information on websites in both unclassified and secure environments continue to expand the reach of sea services but similarly provide vulnerability vectors that may be exploited if not protected. Over the next ten years, a division officer can expect to see the expanding importance of cyber tools, increased need for cooperation among nations operating in shared maritime areas, and more autonomous operations where commander's intent must be fully understood and executed should networked operations be unavailable. Combined Navy and Coast Guard assets such as the Littoral Combat Ship (LCS) and Fast Frigate (FF), the National Security Cutter, the Zumwalt-class guided missile destroyer (DDG), and the Joint Strike Fighter (F-35) will enable highly networked operations, placing even greater emphasis on the importance of skilled and capable officers leading divisions at sea. Despite the technological advances in the tools available to leaders, a great constant remains-the direct personal impact that the division officer has on sailors each day. A division officer's fundamental task is to build the core elements of a winning team. Division Officer's Guide Twelfth Edition is written to reinforce the skills and competencies at the heart of this charge.