During his first major TV interview with ABC’s David Muir, President Donald Trump to protect refugees escaping the violence that has displaced hundreds of thousands of people since the country’s civil war began in 2011. He has requested that the State Department and the Pentagon draw up a proposal within three months.

Per usual, Trump provided no details of how he would actually enforce it. The words “safe zone” were thrown around regularly during the 2016 presidential campaign, but it is doubtful if the average America knows what they are, how they are supposed to function and, , tend to not work very well.

First, the basics. A safe zone is a reserved area for noncombatant parties and transit vehicles to pass through safety without concern for being marked as an enemy combatant. Nations that are in conflict with each other, in theory, are supposed come to terms on where the safe zone is set up, who can pass through, and, most importantly, not to attack it. These locations require significant military resources, finances and highly coordinated communications between conflicting states and aid organizations on the ground.

One problem with setting up safe zones is getting combatant states to agree not to fire on civilians. That is a tough proposition to broker, given that one of the primary purposes of many wars is to kill off as many innocent people as possible, especially if the conflict is a religious or ethnic one. Fighters are rarely, if ever, the only targeted parties in battle.

Take the 1990s war in Bosnia, for example. The international community marked off safe areas for Bosnians to protect them from the Yugoslavian National Army and Serbian paramilitary forces. It failed miserably, primarily because the intent of the aforementioned armies was the genocide of Bosnian Muslims. U.N. peacekeepers were sent to Bosnian safe zones to fire back at soldiers in violation of safe zone rules. Dutch peacekeepers stood by as Serb and Yugoslav soldiers men and boys in Srebrenica in 1995. And had the soldiers shot back, their actions would have pulled them into the war.

Setting up a safe zone in Syria could all but pull America into a war with Syrian President Bashar al-Assad’s government forces, who would most likely attack them. This is one reason why former President Barack Obama against safe zones and significant military engagement.

“As a practical matter, sadly, it is very difficult to see how it would operate short of us being willing to militarily take over a chunk of that country,” Obama said during a news conference in Hanover, Germany, last April, according to . “And that requires a big military commitment” to protect refugees from attacks.

He has also said that Putin’s military actions in Syria would amount to a .

If Trump is serious about a safe zone in Syria, he would have to commit a sizable number of U.S. troops on the ground to protect it. And even if the operation is successful, it would also have to stay to keep displaced populations safe. That is a long-term commitment and an expensive one.

Speaking of money, former Joint Chiefs of Staff Gen. Martin Dempsey testified before Congress in June that the monthly costs as much as $1 billion per month. Thousands of U.S. ground troops would be needed to back up those defending the zone. What if troops are injured? They would have to be extracted, creating new problems for Washington.

Another issue with creating safe zones in Syria is that the U.S. would have to coordinate with Moscow on ensuring fleeing Syrians’ safety. Human rights organizations accuse Russia and Syria of and former Secretary of State John Kerry for a war crimes investigation of Russia.

Helicopters are not known for being the most useful bombing platforms, but some of Russia’s combat…

Then comes the most important factor: Russia, Assad’s military patron, and Turkey both the U.S. involved (remember, the Pentagon says that joint mission this week ) with Kremlin spokesperson Dmitry Peskov saying Russia wasn’t consulted and to “weigh all possible consequences” of such a move. The Russians and Turks recently to a cease fire earlier this week, though the details of how that would work were not publicly discussed.

If it is true that Trump did not speak with Russia or Turkey, the biggest players in the region, then that is a the beginning of a bad route to a successful safe zone. If Turkey and Russia are not on board with Trump’s proposal, it’s dead before it even starts.

Safe zones are well intentioned, but they are extremely dangerous, expensive and complicated operations for the parties who elect to enforce them. So if Trump is really serious about safe zones, he’d better have a long-term plan of what he wants to gain from it. Otherwise, it will be added the list of safe zone plans that failed.