General Mark Milley, the chairman of the Joint Chiefs of Staff, said terrorist groups like al Qaeda could reconstitute in Afghanistan sooner than the original estimate of two years. Christina Ruffini has more. "CBS Evening News with Norah O'Donnell" delivers the latest news and original reporting, and goes beyond the headlines with context and depth. Catch the CBS Evening News every weekday night at 6:30 p.m. ET on the CBS Television Network and at 10 p.m. ET on CBSN. Subscribe to the “CBS Evening News" YouTube channel: http://bit.ly/1S7Dhik Watch full episodes of "CBS Evening News”: http://cbsn.ws/23XekKA Follow "CBS Evening News" on Instagram: http://bit.ly/1T8icTO Like "CBS Evening News" on Facebook: http://on.fb.me/1KxYobb Follow "CBS Evening News" on Twitter: http://bit.ly/1O3dTTe Download the CBS News app: http://cbsn.ws/1Xb1WC8 Try Paramount+ free: https://bit.ly/2OiW1kZ For video licensing inquiries, contact: [email protected]