Longtime U.S. diplomat Richard C. Holbrooke was a towering figure in foreign policy whose skill in resolving conflicts will be missed acutely.

Holbrooke died Monday at age 69 from complications from surgery to repair a torn aorta. At the time of his death, he was serving as President Obama's chief envoy to Afghanistan and Pakistan.

Beginning with Vietnam in the 1970s, Holbrooke served four Democratic presidents over 40 years to help establish national-security strategy. His greatest achievement was brokering the 1995 Dayton Peace Accords, which ended the war in Bosnia.

He accepted the most difficult jobs, and thus seemed a natural choice by Obama to negotiate the complex challenges in Afghanistan and Pakistan. Holbrooke spent the last two years trying to persuade allies to promote economic development there.

Sen. Bob Casey (D., Pa.), chairman of the Senate subcommittee on foreign relations for South Asia, called Holbrooke "tirelessly dedicated to the security of the United States and its allies."

His passing also highlights the uncertainty about our nation's unfinished work in Afghanistan. Fostering a viable central government and economy in Afghanistan has been much more elusive than military success.

And without economic and political stability in Afghanistan, U.S. involvement seems destined to drag on. Obama and NATO have agreed to extend the military presence there until 2014.

Holbrooke also fought hard to secure economic aid for Pakistan, knowing that its stability is vital to efforts to rout Islamist insurgents from the border region.

Holbrooke was a larger-than-life figure on the world stage. His passing leaves a void at a critical moment in U.S. foreign policy.