Level 39

Total Experience Required 279,641 [confirmed]

Level 100 progress: 4.1%

This is roughly:
Killing 933 people in Warzone, or...
Killing 952 people in Execution, or...
Killing 790 people in Wingman, or...
Scoring 199,744 points in Guardian, or...
Scoring 607,916 points in Annex, or...
Scoring 367,949 points in Submission.

Horde (TU4)

Completing 1,399 waves on Casual, or...
Completing 933 waves on Normal, or...
Completing 700 waves on Hardcore, or...
Completing 560 waves on Insane.

Or a combination of the above. Have fun!