Since the 9/11 attacks, U.S. policy-makers have shown a renewed appreciation for the importance of homeland security and how it fits into our defense of the nation as a whole. But this appreciation doesn't always translate into action.

Take the Quadrennial Defense Review (QDR) that Congress mandates for the Department of Defense (DoD). It has yet to establish any such requirement for the Department of Homeland Security (DHS), or to create a means to review how the two departments fit together in the overall national security effort.

By clearly defining agency functions, both the DoD and DHS can minimize overlap and focus on known responsibilities. Furthermore, such an overview would define the security roles of agencies beyond DoD and DHS and help ensure they don't perform duties better carried out by other governmental entities.

The QDR has been used to shape and explain defense policies, military strategy, decisions about how our forces are structured and resources allocated. Yet, three significant problems still plague the QDR process:

• Congress doesn't receive an independent assessment of the Defense Department's analysis. In conjunction with the first QDR, Congress created a National Defense Panel, an independent panel of defense intellectuals and national security experts, to review the results. No such independent assessments have been required of the two QDRs since, and none will be forthcoming later this year, when the Pentagon completes its fourth such review.
  
• The QDR leads Congress and the administration to place too much emphasis on military instruments to meet national-security challenges at home and abroad. Expanding the process to homeland security and its relationship to the defense apparatus would ensure that all U.S. national security instruments are adequate, complementary and properly integrated.
  
• Even when the QDR identifies areas in need of improvement, DoD alone can't say how national security issues should be addressed across multiple agencies nor influence how other federal agencies should change to meet these challenges.

The National Defense Panel provided an overall assessment of the nation's national security during the first QDR. But since then, defense reviews and assessments of other security needs have not been linked.

The failure to do so can be deadly. In 1998, President Bill Clinton's administration and Congress established a U.S. Commission on National Security/21st Century to conduct a broad national assessment similar to the National Defense Panel. But the commission's reports weren't linked to the QDR. Its results were largely ignored - even though it predicted terrorist attacks on the scale of 9/11 and foresaw the need for a Department of Homeland Security.

Nowhere is the need for a detailed assessment on the scale of the QDR more important than in homeland security. "DHS 2.0: Rethinking the Department of Homeland Security," a report by The Heritage Foundation and the Center for Strategic and International Studies, clearly establishes the need for Congress to re-evaluate DHS roles and resources and how they fit with other federal domestic security efforts.

In addition, Congress needs to undertake a post-9/11 assessment of the nation's security apparatus, particularly U.S. public diplomacy and foreign assistance programs, the defense industrial base, the intelligence community and the use of space. Specifically, Congress should:

• Establish a requirement for periodic reviews for homeland security. Congress should require DHS to conduct quadrennial reviews of the department's strategies, force structure, resources and threat assessments. The Quadrennial Homeland Security review should coincide with the midpoint of the presidential term. The first such review should be tasked to address roles, missions, authorities and resources.
  
• Create a one-time National Security Review Panel. In parallel with the first Quadrennial Homeland Security review, Congress should establish a nonpartisan National Security Review Panel to provide an independent assessment of the security review and an overall assessment of national security programs and strategies. The panel should place particular emphasis on evaluating the compatibility of the security review with the QDR and the state of other essential security instruments such as public diplomacy, the defense industrial base, and the use of space for national security purposes.

We've already seen - and paid - the price for overlooking homeland security. Let's not let that happen again.

James Jay Carafano is a senior research fellow for defense and homeland security at The Heritage Foundation.