(CNN) -- They stowed away on trains, slept in shelters and marched in protests as they trekked across Mexico.
Soon hundreds of migrants from Central America will find out whether it was worth it.
Buses carrying members of the caravan pulled into the border city of Tijuana on Tuesday. And organizers say more will soon be on the way.
Many in the caravan say they plan to turn themselves into US authorities and ask for asylum.
The migrants say they're fleeing violence and poverty in Central America and hope they'll find safety and security in the United States.
But President Trump is already making it clear he's not planning to roll out the welcome mat.
It's been weeks since word of their journey first sparked Trump's ire and spurred a decision to deploy the National Guard to the US-Mexico border.
And as more migrants near the border, it's likely we'll see a new round of political ripples. Here are some key questions to keep in mind:
Wait — didn't the caravan dissolve?
Some individuals and smaller groups have split off along the way. The largest contingent is now much smaller than it was at the outset, when about 1,200 migrants from Central America convened at Mexico's southern border weeks ago. According to a recent head count by organizers, that group now numbers closer to 600.
And that's typical. The annual pilgrimage, a march with religious roots organized by Pueblo Sin Fronteras since 2010, normally shrinks as it travels north.
This year, US and Mexican officials offered different explanations for the group's decreasing size. Trump tweeted that the caravan had "largely broken up" thanks to Mexico's strong immigration laws. Mexico's foreign minister countered that the group dispersed on its own — and that pressure from north of the border had nothing to do with it.
But the bottom line is this: Hundreds of migrants are still in the caravan heading toward the US-Mexico border.
So is there going to be some sort of showdown at the border?
It's actually nothing new to have large groups of Central American migrants coming to the border and asking for asylum. That's been going on for years.
But long before this caravan neared the border, it was already getting a lot more attention than other groups of immigrants have in the past. That's not an accident; organizers created the annual event as a way to draw attention to the plight of migrants.
So suffice it to say, neither side has much of an interest in this proceeding quietly, the way many other asylum cases do.
Trump tweeted Monday morning that he'd instructed his head of Homeland Security "not to let these large Caravans of people into our Country."
Hours later, federal officials announced plans to send more asylum officers, prosecutors and immigration judges to the border.
"If members of the 'caravan' enter the country illegally, they will be referred for prosecution for illegal entry in accordance with existing law," Department of Homeland Security Secretary Kirstjen Nielsen said in a statement.
Those who turn themselves in and ask for asylum may end up behind bars while officials evaluate their claims "efficiently and expeditiously," she said. And those who don't have a valid claim, she said, will be swiftly deported.
If the migrants weren't allowed to turn themselves in at the border and proceed with their cases, that would likely be met with a swift outcry as well as legal action from immigrant rights groups, who already filed a class-action lawsuit last year accusing US officials of illegally turning away asylum seekers.
Is what the migrants are doing legal?
Yes. It's not illegal to come to another country without papers and ask for asylum. International law requires countries to consider such claims.
While Mexican officials deported about 400 participants in the caravan for violating their country's immigration laws, they gave others 20-day permits to remain in the country.
The government also gave some migrants the option of seeking asylum in Mexico, setting up information tables at caravan stops to help guide them through the process. Some decided to accept the offer and now plan to stay.
Those continuing north insist they're not planning to sneak across the border. They intend to turn themselves in and ask for asylum.
"People who have a legitimate fear of persecution under US law have a right to present their case," Rep. Zoe Lofgren told reporters Monday. "That's not a violation of immigration law. That's a part of immigration law."
Lofgren, the top Democrat on the House subcommittee on immigration, accused Trump of using the caravan to stir up hatred.
"I think that the President has tried to fan fears of the other," Logren said, "through misstating what this group is about."
What does it mean to ask for asylum?
Asylum is a protected status that allows people fleeing persecution to live legally in another country. But it's not easy to obtain. In order to qualify for asylum in the United States, applicants must prove they have faced persecution in the past or have a well-founded fear of persecution due to their race, religion, national origin, political opinion or membership in a particular social group.
What are the chances migrants in the caravan will get asylum?
Pretty slim. But it's impossible to predict how any one case will go. A number of factors contribute to whether someone wins asylum, including how much evidence they have with them to prove their case and which judge is hearing it.
Looking at national statistics gives a good sense of how tough those cases can be to win — particularly for people from Central America, who often have a hard time meeting the requirements.
More than three quarters of immigrants seeking asylum from El Salvador, Honduras and Guatemala between 2011 and 2016 lost their cases, according to immigration court statistics published by Syracuse University's Transactional Records Access Clearinghouse. That means more than 75 percent were refused.
A large number of people in this year's caravan are from Honduras. Among the reasons they've given CNN for fleeing the country: widespread gang violence, domestic violence, poverty, political repression after a contested presidential election, and discrimination against the transgender community.
Is the current asylum system working in the US?
Not at all, according to critics on both ends of the political spectrum.
Immigrant rights advocates argue the system is engineered to send as many people back to their home countries as possible, no matter what threats they face.
The Trump administration has taken a stance long advocated by immigration hard-liners, who argue that existing asylum procedures in the United States are rife with loopholes that essentially give people who claim fear of persecution a free pass into the country.
"This system is currently subject to rampant abuse and fraud," Attorney General Jeff Sessions said in October. "And as this system becomes overloaded with fake claims, it cannot deal effectively with just claims."
Recently, Sessions has taken steps to exert his authority over the immigration courts and change the way asylum cases are decided.
Advocates maintain that the vast majority of asylum claims are legitimate, and that stacking the deck against immigrants fleeing dangerous situations is immoral and contrary to international law.
What happens to the caravan once it reaches the border?
We won't know for sure until they get there. But asylum seekers generally follow a few steps once they're in custody:
• A credible fear screening: This interview with an immigration official is the first step in the asylum process. If an asylum officer finds that a person's fear of persecution is credible, the case is referred to an immigration judge.
• Detention: This could last for days, months or even years, depending on the case. Adults traveling alone could be transported to detention centers across the United States. Families are most likely to be held in Texas, where there are two family immigrant detention centers.
• Immigration court: This is where asylum seekers will make their case, often facing tough odds. And there's no guarantee they'll have lawyers to help them. In these administrative courts, immigrants don't have a right to an attorney.
• Release from custody: Sometimes, people with pending asylum cases are released on parole. Sometimes, they remain detained until their cases are complete. Advocates recently sued the Trump administration, arguing that adult asylum seekers are now being detained at an alarming rate to deter others from seeking refuge in the United States.
Trump has decried the practice of letting immigrants with pending cases leave detention — and he's vowed his administration will put an end to the policy, which he derides as "catch and release." But officials haven't revealed publicly what they plan to do when this group of Central Americans arrives.
In recent months, immigrant rights groups have accused the Trump administration of separating immigrant parents from their children as they await asylum proceedings. Officials have said they separate adults from children in custody only "in the interest of the child" — for instance, if there's a suspicion of human trafficking or if they are unable to confirm the child is traveling with parents or legal guardians. The Department of Homeland Security's inspector general is investigating the matter.
If immigrants in the caravan lose their asylum cases, the government can order their deportation. If they win, they'll be allowed to stay. But no matter the outcome, it's a long road, filled with uncertainty.
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