During the Cardassian Occupation of Bajor, he was a member of the Ornathia resistance cell where he once led a raid on Pullock V, a Cardassian planet. It was the first off-world raid against the Cardassian Union. During the Occupation, his brother was freed from the Gallitep labor camp by Kira Nerys and the Shakaar resistance cell.
After the Occupation ended in 2369, he joined the Bajoran Militia and by 2371, he had risen to the rank of colonel. Later that year, he led the several troops in Dahkur Province on a mission to find Shakaar Edon and the rest of his resistance cell, which had defied Winn Adami by not returning several government-owned soil reclamators. Winn had ordered the Militia to take over the search from the civil police. Lenaris later agreed with Shakaar that Bajorans fighting each other could lead to a violent civil war and so stood down his forces. He later consulted with his fellow officers, who agreed to support Shakaar in the election for First Minister. (DS9: "Shakaar")
Background information Edit
The script for "Shakaar" describes Lenaris as a veteran military officer, having "been in too many combat situations to be taken aback by anything" when he is surrounded by Kira and Shakaar's men. 
Lenaris appears in the DS9 relaunch novel Unity, where he is one of the top officers in the Bajoran Militia holding the rank of general. He was also one of the signatories to Bajor's admittance into the Federation.