In 1947, British rulers sliced a giant Indian empire into two new countries: a Hindu-majority India, which celebrates its independence Tuesday, and Pakistan, home to mostly Muslims.
Pakistan marked the occasion at midnight, with the the country's top ranking military official General Javed Qamar Bajwa hoisting a huge flag, 120 feet by 80 feet, at the Wagah border crossing, at the demarcation line with India.
Fireworks lit up the sky at midnight as the day's celebrations officially began, but for the past week all of Pakistan's major cities have been decked out with the green and white national flag and lights and bunting of the same colors.
The country will also host the largest ever air show in the capital, Islamabad, where aerobatic teams from Turkey and Saudi Arabia will participate along with the Pakistan Air Force. Pakistani security forces will also share sweets with their Indian counterparts at the border.
India's celebrations will go into high gear Tuesday with Prime Minister Narendra Modi set to address the nation.
The partition of India and Pakistan ended two centuries of British colonial rule and saw one of the largest human migrations the world has ever seen.
The border, cutting through Bengal in the east and Punjab in the west, was confirmed two days after India became independent. A line was quickly marked on maps using censuses of "minority" and "majority" populations.
An estimated 12-15 million people left their homes and crossed the new border based on their faith -- Muslims to Pakistan, while Hindus and Sikhs took the opposite journey.
At least a million people died in communal attacks as they crossed the border and tens of thousands of women and girls were abducted and raped.
This hastily drawn line and the violence that followed continues to plague ties with India and Pakistan to this day.
The two nations have fought four wars since 1947 mostly due to disputes over the northern Himalayan state of Jammu and Kashmir, which both countries claim total control of.
Attempts to renew dialogue and restore peace have been made numerous times but for now relations between the nuclear-armed neighbors still remain hostile.