Army Major Nikhil Handa exchanged more than 3,500 calls and messages since January with the officer's wife he is accused of murdering, it was revealed in court on Monday.
Shailza Dwivedi, the wife of another major, was found at the Delhi cantonment area on Saturday with her throat slit and signs of being run over.
Major Handa, arrested from Meerut near Delhi on Sunday, was sent by a court to four-day police remand.
The officer allegedly slit Shailza Dwivedi's throat with a knife after an argument in the car. He was obsessed with her and wanted to marry her.
"Judging by the number of calls he made, he was too possessive about her," said police officer Vijay Kumar.
When Shailza Dwivedi, a beauty contest finalist, refused him, Major Handa allegedly slashed her throat. Then he pushed her off the car and ran her over to make it look like a hit-and-run, the police suspect.
The murder weapon has not been found.
The police have learnt that Major Handa had fought with his wife over his relationship with Shailza Dwivedi the previous night. On Saturday, he had called Shailza and arranged to meet with her when she was out on a shopping trip.
After the murder, he reportedly took his Honda City car for a thorough cleaning but forensic experts were still able to detect traces of blood.
The police say Major Handa also tried to get rid of her phone by breaking it to pieces and dumping it in a trash can near his home, but it was found.
"We have fingerprints and Shailza's hair from the car. Handa also deleted many apps from his and her phones. We are trying to retrieve them," said a police officer.
CCTV footage from outside the Army Base Hospital in the cantonment showed Shailza getting into a car, not long before her body was found in the area.
Major Handa and Shailza Dwivedi met in 2015 in Nagaland when her husband was posted there. They had kept in touch even when she came to Delhi after her husband's transfer.
Major Handa, currently posted in Nagaland's Dimapur, was arrested after Major Amit Dwivedi revealed his suspicion to the police.