Amphibious ships have been called the “Swiss Army Knives” of the sea and America’s “911 force.” They are versatile and responsive, making them one of the most valuable assets of the U.S. Navy and Marine Corps. That is why we turn to them time and again – from major combat missions to humanitarian assistance and disaster relief.

Unfortunately, many of our country’s amphibious warships are approaching or have exceeded the end of their expected service lives. The military is retiring ships faster than it can obtain new ones – a consequence of reduced funding, longer at-sea periods, and higher maintenance and modernization costs. This reality of an aging fleet raises serious concerns about America’s preparedness in a world of increasingly diverse and complex threats.

The current size of the Navy’s inventory only adds to these concerns. At 29 vessels, our amphibious fleet falls far short of the Marine Corps requirement for 38 ships. Earlier this year, Chief of Naval Operations Adm. Jonathan Greenert told the House Armed Services Committee that “We probably need 50 [amphibious ships]. If we want to do everything that we’re asked to do.” Navy plans, however, do not foresee a fleet of even 33 ships until at least a decade from now.

To be sure, today’s budget constraints have presented difficult challenges for all departments, not just defense. They certainly implore us to find the most efficient and effective use of our resources in responding to national priorities. Ensuring that these resources are used wisely demands an honest assessment of America’s future security risks as well as the growing role of sea-based precision strikes and involvement of special forces. If we truly want to project U.S. power, as the Obama Administration has proposed with its defense pivot to the Asia-Pacific region, we must equip our Combatant Commanders with a capable and ready force.

Amphibious warships send a powerful signal to our adversaries and allies that America’s military remains strong. The United States maintains the largest and most advanced amphibious fleet in the world. These warships can transport specialized forces to areas of conflict or disaster – both far inland and directly ashore – with accompanying ground, air, logistics, and command and control elements for sustained operations. They are also often the first to respond in the event of a terrorist act or natural disaster. We saw this in the aftermath of Hurricane Katrina, when amphibious ships were used for relief duties on the Gulf Coast. Before that, they provided humanitarian support after the devastating Indian Ocean tsunami in 2004.

It is clear that the demand for a resilient amphibious force is not likely to go away anytime soon. In a recent letter to the Senate Armed Services Committee, 20 retired generals and lieutenant generals called amphibious ships “the cornerstone of America’s visible forward presence.” They noted the breadth of responsibilities entrusted to our amphibious fleet, including air and ship crew rescues, counter-piracy operations, embassy reinforcement, and naval support for our allies. They warned that a diminished and outdated fleet could have a negative impact on America’s national security objectives well into this century.

The lessons of the 2012 terrorist attacks on Americans in Benghazi are a tragic reminder of the need for constant vigilance and preparedness. Violent extremism remains a persistent threat, demanding immediate action when Americans are in harm’s way. Amphibious forces not only offer a way to counter these threats but also play a critical role in deterring potential aggression before it happens.

In a Senate Armed Services Committee hearing this year, Marine Corps Commandant Gen. Jim Amos pointed to the gap in operations in the Mediterranean as an example of why additional warships are necessary. One could hardly argue that U.S. interests have faded there, given the recent instability in Libya, Egypt, and Syria. Unlike today, amphibious forces were a regular presence in the Mediterranean in the late 1990s and early 2000s.

I join our current and retired military leaders in supporting efforts to advance America’s amphibious capabilities. We must find cost-efficient ways to streamline our fleet and address the needs of our Navy and Marine Corps. Our fighting forces deserve dependable and modern equipment when defending America in dangerous and hostile parts of the world.

This op-ed appeared in the Washington Times on May 28, 2014.