For Ban Ki-moon, the United Nations secretary-general, the global humanitarian crisis is personal. 

As a 6-year-old boy, the Korean diplomat was uprooted from his village and school by the Korean War. It was the lifeline extended to him and his family by a fledgling humanitarian system and a nascent United Nations – shelter, food, schoolbooks – that allowed that small boy to prosper, Mr. Ban likes to say.

Six decades later, his push to overhaul the international humanitarian system – marked by the first-ever World Humanitarian Summit in Istanbul, Turkey, starting Monday – is also personal.

The world faces the largest population of refugees and other displaced people since World War II, and Ban’s tenure up at the end of this year.

Already, he has overseen the Paris climate change accord and the Sustainable Development Goals. Both of those agreements were seen as new ways of thinking about the key challenges facing the 21st century.

Now, Ban’s childhood experience – both the trauma of displacement but also the way the international community gave one little boy “hope for the future” – has prompted him to make a reinvigorated humanitarian system the third piece of his agenda, aides say.   

But the “fundamental change” that Ban is looking for is promising to be every bit as difficult as were the climate and development agreements.

Not only does the summit seek to reform an entrenched, top-down system of billion-dollar interests, but the run-up to the meeting has been beset with controversy. No-shows have garnered more attention than the pre-summit reform initiatives.

Russian President Vladimir Putin has declined an invitation and pledges not to be bound by its outcome, saying organizers’ discussions about humanitarian interventions are disregarding national governments’ interests.

The global aid group Doctors Without Borders has also pulled out of the summit, claiming nothing is being done about rising attacks on humanitarian facilities such as its hospitals in conflict zones. The group also worries that the summit will rubber-stamp a shift of emergency-response funding to longer-term development efforts.

The snubs represent the polar ends of an intensifying international debate about the power of national governments in overseeing humanitarian interventions.

The nationalist Putin – who has targeted international humanitarian and rights groups in Russia – says envisioned reforms would diminish the role of governments  “in the conduct of humanitarian assistance.”

On the other hand, Doctors Without Borders wants action against the states it says are responsible for a significant piece of the humanitarian crisis. Last year alone, 75 of the hospitals it manages or supports were bombed, it says. The summit is “a fig leaf of good intentions, allowing these systematic violations, by states above all, to be ignored.”

Beyond such controversies are profound differences over how the humanitarian system should change – or whether an overhaul is even necessary.

Some organizations insist the system is meeting more needs than ever before – and isn’t coming up short in any way that money can’t fix. Noting that the UN’s 2015 Global Humanitarian Appeal was only about half funded, this faction will attend the summit proclaiming that the system is “broke, not broken.”

But for those seeking change, a few questions will loom large.

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One is the potential devolution of more responsibility to local organizations and actors. Advocates say a system developed at the close of the colonial era by Western powers no longer serves in a world of 195 independent nations. It fails to tap the grass-roots organizations already on the ground where most humanitarian disasters arise, they add.

Some of the most ardent proponents of the “go local” trend are in developing countries. Individuals and groups in this Global South say the established powers can no longer justify monopolizing the purse-strings and decision-making for efforts in their regions.

Some “northern” organizations are joining in. The Britain-based Humanitarian Policy Group pointedly named its pre-summit report “Time to Let Go.” It says UN agencies, government aid institutions, and private humanitarian organizations need to give up much of the managing and focus on supporting local counterparts.