Operation Zarb-e-Azb was carried out after the tragic attack on a school ending with massacre of innocent kids by TTP (Tehreek-e-Taliban Pakistan)
PML-N won the general elections of 2013 in Pakistan. Nawaz Sharif the PM of Pakistan was a strong supporter of peace dialogues with militants, that's why his government took serious steps for dialogue and offering huge compensation to former Taliban to join the main stream and give up anti-state activities.
These deeds were harshly criticised by Liberal side of the country. After 6 months of a useless period of dialogue, Taliban conducted an attack first at Karachi airbase and on 16th December 2014 on APS Peshawar killing 140+ innocent students. This incident shook the whole world and a huge pressure emerged from public on the army and government to eliminate all sort of terrorists from their havens. Pakistan never conducted operations in North Waziristan (complex hilly area like Tora Bora in Afghanistan) even after huge pressure by US and Nato.
After the APS attack
The Pakistani establishment after the attack decided to carry out a grand operation mainly based on intelligence reports within country and on-land operation to clean up in North Waziristan valley.
This operation was covered by NAP (National Action Plan) which included several reforms and in-time tough decisions like forming military courts and removing the ban on sentencing by hanging.
2 years of success in the most complex region and safest haven for terrorists
From June 15 2014 to June 15 2016 Pakistan Army wiped out all sort of militants by clearing the 100% of valley which was globally considered impossible by critics to be cleaned from terrorists. After 2 years of Operation Zarb-e-Azb there's a significant decrease of upt o 70% in terror attacks in the country. Global Terrorism counter indexes includes The Global terrorism index (GTI) & South Asia Terrorism Portal also acknowledged the success of Zarb-e-Azb and significant reduction in casualties after 2 years of the successful operation.