Today, Feb. 4, President Barack Obama will host Colombian President Juan Manuel Santos at the White House Rose Garden to commemorate 15 years of Plan Colombia. The Colombian president arrives to Washington just months ahead of an historic peace deal with that nation’s armed insurgency, the Revolutionary Armed Forces of Colombia, known by their Spanish acronym FARC.

Santos will need to persuade United States legislators and officials to stand in partnership with Colombia as peace approaches, just as the U.S. has supported Colombia through decades of war. U.S. assistance has been efficacious in leading to this moment: Plan Colombia, a $10-billion development and security aid plan, was instrumental in weakening the guerrillas and convincing them to join the government at the negotiating table.

To capitalize on these gains and to consolidate peace, President Santos will need buy-in from the international community. This week the United Nations approved a mission to oversee a bilateral ceasefire and monitor the implementation of the peace deal. That’s a start. But a weakened peso and shrinking GDP have put the Colombian government’s $92 billion-dollar post-conflict development plan in jeopardy. The U.S. government should ensure that Santos’ Plan for Peace does not fail. The benefits of a Colombia at peace are wide ranging and will affect the entire hemisphere.

First, peace with the FARC would offer the U.S. government long-sought-after gains in the War on Drugs. The FARC are Colombia’s principal cocaine producers and primary link with the Mexican Sinaloa Cartel. Former Colombian President Andres Pastrana recently asserted that their joint enterprise generates upwards of $30 billion in ill-begot wealth a year. When the FARC lay down their arms, a number of rival drug gangs will be eager to lay claim to their lucrative operations and assume control of their drug routes. Only a robust post-conflict security plan will ensure that the state, not criminals, wrest control of the power vacuum left by the demobilized guerrilla force. In this vein, the U.S. government should also suspend drug warrants against guerrilla commanders who have renounced drug production and trafficking and have agreed to provide valuable intelligence to U.S. and Colombian authorities.

Second, U.S. assistance can once and for all help address the underdevelopment and social exclusion that fuel illegal activity in rural Colombia. Last July Santos launched an ambitious National Development Plan to enhance infrastructure and fund social programs in Colombia’s hinterlands. FARC rank and file and their families stand to benefit most from this investment, but by Santos’ own admission, his strategy currently falls short $7 billion for the first year of post-conflict alone.

Third, U.S. support for post-conflict would send a strong signal to the Colombian and international business communities. Colombian citizens willingly shouldered a large tax burden to support the government in taking the fight to the FARC more than a decade ago. In fact, the Colombian government outspent U.S. aid investments to Plan Colombia by a factor of four. These same Colombian citizens must now be convinced to match international contributions to peace and, just as importantly, hire and train a stigmatized and poorly educated labor force. Failing to do so would all but ensure that droves of guerrilla fighters return to criminality.

Lastly, a U.S. aid package would serve as recognition of the valuable support that Colombia has delivered on a number of U.S. foreign policy objectives. Santos played a critical role in opening lines of communication between the U.S. and Cuban governments. Colombia has also deployed counternarcotics and counterinsurgency advisers to assist the NATO-led coalition in Afghanistan, and at present, Colombian police and judicial teams are dispatched across Central America to support U.S.-led missions focused on strengthening rule of law in that region.

The Colombian people have proven their loyalty to a mutual vision of peace far beyond Colombian borders. And so far, the U.S. government has gotten its Colombia strategy right: Plan Colombia represents the rare, successful U.S. policy initiative that enjoyed broad bipartisan support across five U.S. presidential terms.

But our work is not yet done. The recent lessons of Iraq and Afghanistan have demonstrated the perils of prematurely declaring victory on foreign shores, where investments in development and reconciliation are every bit as essential as military hardware and training. The spirit of partnership and cooperation that has long characterized our work in Colombia should, no doubt, be reflected in U.S. aid commitments to Mr. Santos’ post-conflict vision. If not, the hard-won gains of the past 15 years are, much like the positive legacy of Plan Colombia itself, at serious risk of disappearing.

Angelo is an International Affairs fellow at the Council on Foreign Relations. He is a graduate of the U.S. Naval Academy at Annapolis and received a master of Philosophy in Latin American Studies at the University of Oxford, where he was a Rhodes Scholar. During his nine-year career in the U.S. Navy, he deployed multiple times to Colombia as an adviser to the Colombian Armed Forces. The views expressed in this opinion piece are those of the author alone and do not reflect the views of the U.S. government or the Council on Foreign Relations.