Step 1: China's Invasion
The first event that occurred was China's massive invasion in 1962, which led to the brief border war between China and India.
Step 2: Aksai Chin Occupation
After the invasion, China occupied the Aksai Chin region, which was a part of the territory disputed between India and China. This occupation was a significant event in the bilateral relations.
Step 3: Restoration of Diplomatic Relations
Full diplomatic relations between India and China were restored after years of strained ties, particularly after the 1962 war. Diplomatic channels were reopened to stabilize the relationship.
Step 4: Atal Behari Vajpayee's Visit
In 2003, Atal Behari Vajpayee, the then Prime Minister of India, became the first top-level Indian leader to visit China after the restoration of diplomatic ties. This visit was a landmark in the diplomatic history of India-China relations.
Step 5: Final Answer
Thus, the correct chronological order is (A), (D), (B), (C).