In the House, the Armed Services Committee writes the laws which authorize the Department of Defense to take such actions as the Congress deems necessary to ensure the security of the United States.  One of the main issues with which the Armed Services Committee concerns itself is authorizing the Department of Defense to spend money to fulfill the responsibilities Congress gives it.  This includes military construction, pay and benefits for members of the military, and the procurement and maintenance of equipment and weapons systems.

Once the Armed Services Committee has authorized an expenditure, though, it remains for the House Appropriations Committee to actually provide the funds from the U.S. budget to enable the Department of Defense to spend the money it has been authorized to do so by the Armed Services Committee.  The agreement of both committees is therefore usually necessary for the Department of Defense to undertake any activity requiring the expenditure of significant amounts of money.

An identical arrangement exists in the Senate as well, where the Senate Armed Services Committee authorizes actions and programs, but the Senate Appropriations Committee must actually allocate the money to the Department of Defense to carry out the actions authorized by the Armed Services Committee.

When legislation authorizing a new defense program and additional legislation funding it is passed by both Houses of the legislature and signed into law by the President, the Department of Defence is then able to proceed to actually sign contracts and allocate the funds necessary to develop the system.  The cycle of authorization and funding followed by Department of Defense studies, testing, evaluation and production typically is several years long, requiring a high level of planning and management by all concerned to bring a new program to successful deployment.