Pakistan launched airstrikes on major Afghan cities overnight on Thursday, in a move that has been fueling months of border clashes between the Islamic neighbors. Meanwhile, Pakistan declared open war on Thursday.

Pakistan said it had retaliated by attacking Taliban military posts, headquarters and ammunition depots in the border areas after Afghanistan launched an attack on its border forces.

Both sides have said they have suffered heavy casualties in the fighting. A large number of soldiers were killed in fighting along the border between the two countries in October. At that time, Turkey, Qatar and Saudi Arabia called for a ceasefire. However, it could not be implemented.

After the Taliban took over Afghanistan in 2021, there was initially no conflict between the two sides. Pakistan welcomed the Taliban's return to power. The then Pakistani Prime Minister Imran Khan said that Afghans had 'broken the bonds of slavery'.

Pakistan had sought Afghan help to control radical Islamic groups in its country. However, this support was not possible from the Taliban, which seized power under the guise of radical ideology.

The latest dispute between Pakistan and Afghanistan is over the Tehreek-e-Taliban Pakistan (TTP). It is also called the Pakistan Taliban. It was formed in 2007 by Islamic armed groups active in northwest Pakistan. The TTP has attacked markets, mosques, airports, military bases, and police posts in Pakistan.

It has captured many areas along the border with Afghanistan. Similarly, it also controls Pakistan's Swat Valley. In 2012, the same group attacked schoolgirl Malala Yousafzai. She was awarded the Nobel Peace Prize two years after the incident.

The TTP fought alongside the Afghan Taliban against the US-led forces in Afghanistan. In the process, it had sheltered Afghan militants in its base areas in Pakistan. Pakistan had launched a military operation against the TTP. However, it was not successful.

The Islamists accuse the TTP leadership and many of its fighters of living in Afghanistan and carrying out violent activities in Pakistan. Similarly, it alleges that armed insurgents seeking independence from the southwestern Pakistani province of Balochistan have also used Afghanistan as a safe haven.

According to the global monitoring organization, Armed Conflict Location and Event Data, attacks by the TTP and Baloch insurgents have been increasing every year since 2022.

Afghanistan has denied the Islamists' allegations. It has claimed that its soil will not be used against Pakistan.

The TTP claimed responsibility for a suicide attack in Bajaur district last week that killed 11 security personnel and two civilians. Pakistan has since accused Afghanistan of harboring terrorists, a charge Afghanistan has denied.

Analysts say Pakistan is likely to step up its military campaign. Pakistan's army is much larger than Afghanistan's. With around 660,000 active troops, Pakistan is the seventh largest military power in the world. There are only 75,000 active troops in Afghanistan.