This is the first time that the club from Shillong -- who also emerged champions of 2nd Division I-League with 19 points from 10 outings -- will take part in the I-League first division.
They won all their matches in the second round of the final phase of 2nd Division I-League.
The closest Rangdajied had come to qualifying for the I-League first division before this year was in 2011 when they had finished fourth in the final phase and narrowly missed out from the 2011-12 I-League season.
Restom Khriam doubled the lead at the stroke of half time after being set up brilliantly by Babatunde Ayomide. Shin Hojun sealed the issue with a solo effort in the 85th minute. Jerry Zirzingha pulled one back for Mohammedan Sporting in the 83rd minute.
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Another Shillong based side, Shillong Lajong FC is playing in the ongoing I-League and they are expected to retain their place in the next edition (2013-14). Shillong will thus have two teams in the I-League 2013-14 season.
"I can't express how happy I am. This has to be the finest hour of the club. We have worked so hard for this day. While we were preparing for the 2nd Division, I remember not allowing the players to go home for a single day. They obeyed, and today we are reaping the dividends. The day has finally arrived. We are going to celebrate a lot tonight," Karsing said.