What's happening in Syria?
US President Donald Trump has ordered missile attacks on Syria, a country in the Middle East.
For the latest on the US airstrikes click here, but for a background on the war in Syria read on.
The war in Syria has gone on for more than six years and has claimed the lives of more than a quarter of a million people.
It is being fought between soldiers who support the president of Syria, Bashar al-Assad, and a group of fighters known as rebels, who don't want him to be in power anymore.
How did it all start?
The trouble began in 2011 in the Syrian city of Deraa.
It began because local people decided to protest after 15 schoolchildren were arrested - and reportedly tortured - for writing anti-government graffiti on a wall.
The protests were peaceful to begin with, calling for the release of the children, democracy and greater freedom for people in the country.
The government responded angrily and, on 18 March 2011, the army opened fire on protesters, killing four people. The following day, they shot at mourners at the victims' funerals, killing another person.
People were shocked and angry at what had happened and soon the unrest spread to other parts of the country.
At first, the protesters just wanted democracy and greater freedom.
But after government forces opened fire on peaceful demonstrations, people demanded that President Bashar al-Assad resign. However, he refused to do this which made the protesters extremely angry.
President Assad still had a lot of people in Syria that supported him and his government, so they began to fight against people who were against the government.
In July 2012, the International Red Cross said the violence in Syria had become so widespread that it was in a state of civil war.
Who are the rebel fighters?
There isn't one single group of rebels fighting against President Assad and the government's army.
The group who want the president to step down - called the opposition - is made up of several kinds of people. These include groups of rebel fighters, political parties who disagree with Assad, and those living in exile who cannot return to the country.
It is thought there could have been as many as 1,000 different groups opposing the government since the conflict began, with an estimated 100,000 fighters.
Is there anyone else involved?
The crisis in Syria has become more than just a war between people who are for or against President Assad.
In 2014, a group that calls itself Islamic State (IS) began to take over large areas of a country called Iraq, next door to Syria.
IS is a militant group with extreme, violent views, which has used this violence against anyone who doesn't agree with what they think. They have also persecuted other groups, including Christians and Yazidis.
They moved into eastern Syria and, in the chaos of the war, they were able to gain land and power there too.
Now, both Assad's forces and the rebels are having to fight a separate battle against IS at the same time.
To try to stop IS, in September 2014 the US used planes to attack IS fighters in Iraq. These attacks are known as airstrikes.
Just over a year later, UK MPs voted in favour of military action against IS in Syria too. The first airstrikes were carried out by RAF Tornado jets within hours of the vote in the House of Commons.
What has been the impact of the war on people living in Syria?
Millions of ordinary people living in Syria have had to escape from their homes to find somewhere safer to live.
According to the United Nations (UN), a group that works to try to solve some of the world's problems, almost five million Syrians have had to leave the country. Many have gone to neighbouring countries, like Jordan, Lebanon, Turkey or Iraq.
Six million more people have tried to find safety elsewhere in Syria.
Lots of children can no longer go to school because their schools have been destroyed or there are no teachers where they have moved to.
When people are forced to leave the country where they live like this, they become known as refugees. The conflict in Syria has caused one of the largest refugee movements in recent history.
Many refugees made the decision to try to reach Europe. This is because some countries in Europe said they would accept refugees who wanted to start a new life here.
Millions of people both inside and outside Syria are in desperate need of help, but aid agencies say that getting help to people inside the country is very difficult and dangerous.
What else do we need to know about this war?
One other topic that has been talked about a lot is the use of chemical weapons.
There is an international law which bans countries from using chemical weapons in wars, as they are deemed too cruel to use on other people.
However, in August 2013, it was reported that they were used in the war in Syria, which caused anger around the world. Both the rebels and the Syrian government denied that they were responsible.
MPs in Westminster voted against responding to this with military action in Syria. But the US and French governments discussed limited missile strikes against military targets.
In September 2013, Russia and the US reached an agreement which said the Syrian government should give up its chemical weapons and destroy them so they can never again be used. This was important as Russia and the US support different sides in the Syrian war.
The process of destroying the weapons began in October 2013 and the people working on this project were awarded the Nobel Peace Prize later that month.
But in April 2017, there was reportedly another chemical weapons attack on a town in north-west Syria, which killed and injured many people.
Many weapons experts, the UK and other countries, and US President Donald Trump have said President Assad's government was to blame for the attack.
But the Syrian President says he didn't do it and Russia, which supports him, said it was the result of aircraft hitting chemical weapons on the ground, which belonged to the rebels.
The US has responded with military action by carrying out missile attacks on Syria, which the UK has said it supports.
So what next for Syria?
It doesn't look like the fighting is likely to end any time soon.
There is a stalemate between the two sides. This means that the government forces and the rebel groups are unable to defeat each other or agree on the future.
Lots of countries are trying to continue to supply aid, such as food and emergency supplies.
The rest of the world will continue to try to work out if there is a way to help Syria achieve peace. But for the time being, the conflict continues.