MADRID — Spanish riot police attacked peaceful protesters in Catalonia on Sunday to try to disrupt a banned independence vote, injuring hundreds as Spain’s constitutional crisis deepened.

Here’s a look at how Spain got to this point:


WHAT IS CATALONIA?

Catalonia is one of Spain’s 17 autonomous regions. Its capital is the dynamic Mediterranean port city of Barcelona, a perennial favorite for tourists.

With a population of 7.5 million inhabitants, it is one of Spain’s main economic powerhouses, contributing a fifth of the country’s 1.1 trillion-euro economy ($1.32 trillion). The region has its own cultural traditions and its own language, which was suppressed during the 1939-1975 dictatorship of Gen. Francisco Franco. It is also home to one of the world’s best-known soccer teams, FC Barcelona.

The regional government runs its own police and exercises considerable powers in health and education, but key areas such as taxes, foreign affairs, defense, ports, airports and trains are in the hands of the Spanish government based in Madrid.


WHY DOES IT WANT INDEPENDENCE NOW?

While many Catalans have long stressed the region’s differences from the rest of Spain, the latest surge for independence began in 2010, when Spain’s Constitutional Court struck down key parts of a groundbreaking charter that would have granted Catalonia greater autonomy and recognized it as a nation within Spain.

The court’s rejection stung the region and has since driven hundreds of thousands of residents out onto the streets every Sept. 11, a Catalan holiday, to demand independence.

Spain’s 2008-2013 financial crisis, and the harsh austerity measures that followed, generated more support for secession, with many Catalans feeling they could do better on their own.


DO ALL CATALANS WANT INDEPENDENCE?

While the vast majority of Catalans favored holding a referendum, they have long been almost evenly split over independence. In recent months, especially with the national and regional economies thriving again, polls indicated support for secession was on the wane, although it would still be a close call.

The region’s first attempts to hold a non-binding referendum in 2014 were blocked by the Constitutional Court. The Catalan government went ahead and staged an unofficial poll. About 2.3 million Catalans — less than half of those eligible — voted, with 80 percent favoring independence.

Regional elections in 2015 returned a slim majority of pro-independence lawmakers, who took this as a mandate to push ahead with the independence drive. They have pledgedthey will proclaim a new republic within 48 hours of the ballot if a “yes” vote wins the new referendum, regardless of turnout.

The Constitutional Court ordered the referendum suspended while it studied its legality but Catalan authorities refused, insisting the region’s desire to vote overrides this.


ARE THE TWO SIDES TALKING?

Talks between the two sides have been virtually nonexistent, with both sides accusing the other of acting illegally undemocratically. Before Sunday’s vote, Spanish conservative Prime Minister Mariano Rajoy had insisted he couldn’t discuss a referendum unless the constitution was changed, and invited Catalonia to work on changing it. The Catalan government said its right to self-determination must be respected first before talks could proceed.

Catalonia was seeking a referendum like those permitted in Scotland and Quebec, but Spain’s 1978 constitution stipulates that only the national government can call referendums on sovereignty and that all Spaniards must be allowed to vote.


COULD CATALONIA SURVIVE ALONE?

Both Spain and Catalonia would likely suffer considerably if they parted ways without agreement. But Catalonia’s fate would also depend on outside reaction.

So far, no country or international body has expressed any appetite for Catalan independence. The European Union, fearful that it could stir other regional nationalists to follow suit, says Catalonia would have to reapply for EU membership, something that Spain could block.

The economic impact is virtually impossible to estimate. Catalonia has a gross domestic product of about 215 billion euros ($257 billion) — the largest of the Spanish regions, greater than Greece’s and close to those of Ireland and Denmark — but many of its goods are supplied by the Spanish state. Spain in return relies on Catalonia’s industrial products and export facilities.