WASHINGTON -- Foreign policy wasn’t the issue that got President Barack Obama re-elected Tuesday, but with upheaval in the Middle East, a war to end in Afghanistan and strained relations with superpowers Russia and China, it’s sure to play an outsized role in shaping his legacy as he enters a hard-won second term.

One of Obama’s first and most crucial tasks will be naming a successor to Secretary of State Hillary Clinton, who’s vowed to step down after this year. Still reeling from his administration’s botched handling of the deadly terrorist attacks on U.S. diplomatic targets in Libya, Obama is no doubt seeking a deft and versatile replacement to guard and advance U.S. interests in a volatile world, especially in the Middle East, where creeping fundamentalism undermines longstanding U.S. influence.

“This so-called Arab Spring has not run its course and, in the short to medium term, and I certainly mean to the end of this decade, I think it’s going to be very tumultuous,” said Richard Armitage, who served as deputy secretary of state under President George W. Bush. “You are going to have volatile, weak leadership governments that are Islamic leaning. That is not necessarily going to end up that way. But it’s going to occupy an increasing amount of our time.”

Among those rumored to be under consideration for the top diplomatic slot are Sen. John Kerry, the Massachusetts Democrat and chairman of the Senate Foreign Relations Committee, National Security Adviser Thomas Donilon and U.N. Ambassador Susan Rice. Rice’s star has fallen somewhat since her role in spreading incorrect information – she says unwittingly – in the aftermath of the Libya attacks that killed Ambassador Christopher Stevens and three other American personnel on Sept. 11.

Clinton’s replacement will inherit headaches in virtually every corner of the world: the unresolved debt crisis in Europe, the rise of militant Islamist factions in transitional Arab states, a nuclear showdown with Iran, a moribund Palestinian-Israeli peace process, trade disputes with China, looming wars in Africa, disagreements with Russia over missile defense and Syria, and a backlash to the U.S. drug war in Latin America.

Here’s a closer look at some of the top foreign policy challenges on the horizon for Obama’s second term:

Syria and the Arab world

The civil war in Syria is the bloodiest offshoot of the Arab Spring rebellions that swept through the region in late 2010 and 2011.

Twenty months into the uprising against President Bashar Assad’s regime, U.S. strategy remains enigmatic. The United States won’t officially arm the rebels, but it supports regional allies pouring weapons into the battlefield. For months, American diplomats bet on a council of exiles to lead the transition before abruptly dumping them last week in search of “broader representation,” especially Syrians actually fighting in the conflict. And yet, U.S. interlocutors still maintain only limited channels to rebel commanders, preferring to deal with the “nonviolent opposition,” who enjoy less legitimacy among Syrians.

Allowing the war to continue without acting to end it quickly and decisively has created a vacuum in the region, which could lead to radicalization and far greater extremist influence in Syria itself and to a regional conflict, drawing in Turkey and possibly other countries.