Nuclear proliferation has been a vexing but important issue for U.S. President Barack Obama during his two terms in office.

Since his election, he has fought an uphill battle in his quest for a world without atomic weapons. Now in the twilight of his presidency and amid a growing debate over the merits of a potential shift to a "no first use" nuclear policy, things aren't likely to get any easier.

As Obama weighs a change in strategic doctrine in the coming days and weeks, to declare that the U.S. would never be the first to use nuclear weapons, Asian security experts, academics and top officials across the globe remain divided over the issue: Is maintaining the first use option an outdated Cold War relic or a necessary evil, crucial for protecting American allies on the continent?