(CNN) Sen. Bernie Sanders is welcoming back a former aide who fell out with his inner circle in the summer of 2016 after she and other staffers resigned from his political organization right as it launched.

Claire Sandberg led the Vermont lawmaker's distributed organizing team during his last primary bid and comes on now as the 2020 campaign's director of organizing -- a senior leadership position traditionally associated with a job title like national field director. The hiring marks an unlikely reconciliation given Sandberg's headline-grabbing departure from Our Revolution, a group formed to keep up Sanders' "political revolution" on the heels of his first presidential campaign.

Sandberg returns to the fold after making peace with Jeff Weaver, Sanders' polarizing former campaign manager and close confidant, who has since moved into a senior adviser role. She will lead what is expected to be a massive, coordinated operation designed to channel Sanders' grassroots support into more proactive volunteer-initiated activities. The decision to hire Sandberg -- who joins Tim Tagaris and Robin Curran, two more 2016 veterans -- to the 2020 team is also a sign of the campaign's determination to retain its top talent from four years ago.

A number of other 2016 aides credited with helping to build Sanders' estimable online presence, including Kenneth Pennington -- who left Our Revolution along with Sandberg -- went on to work for Beto O'Rourke's Senate bid in Texas last year. Some are now expected to take lead roles in the former Texas congressman's recently launched presidential campaign. O'Rourke narrowly outpaced Sanders' first-day fundraising haul, pulling in $6.1 million in the 24 hours after his announcement last week.

"It's no secret that I had my disagreements with Jeff in the past, but a little less than four years later, I look back on the first campaign and I can think of many more things that he did right then that he did wrong," Sandberg said in an interview with CNN. "I think it says a lot about who he is and his commitment to Bernie and to our movement that he was willing to accept my apology and ask me to return despite the history there."

During her time in exile from Bernieworld, Sandberg worked with leftist activists from the UK's Labour Party, Podemos in Spain and Germany's Die Linke, while also serving as deputy campaign manager for Abdul El-Sayed, the young progressive who ran unsuccessfully for the 2018 Democratic gubernatorial nomination in Michigan.

Her role on the Sanders campaign in 2020 is -- like all things Bernie 2.0 -- expected to be considerably larger and better defined than it was four years ago, when the campaign outperformed its wildest expectations early on and, as Sandberg put it, "ran out of runway" by the time the election map expanded beyond Iowa and New Hampshire. By the end of Super Tuesday, Hillary Clinton had staked out a delegate lead that Sanders never had a realistic chance of overcoming, despite notable victories later on in states like Michigan and Wisconsin.

Even with the nomination clearly out of reach, the Sanders 2016 digital and field organizing teams continued to develop and refine their tactics. Those efforts will mostly be streamlined in the new campaign.

Sandberg estimates that the Vermont independent's decentralized volunteer army ended up knocking on 5 million doors and sending out 10 million peer-to-peer texts by the end of the 2016 cycle.

The key, Sandberg said, is in asking supporters to do more than donate and talk up the candidate on social media.

"I think many campaigns see their supporters as an ATM or a source of likes and shares and not as an integral part of the campaign," she said. "We are going to ask a lot of people who believe in Bernie and who also want us to ask them to do things. They want to be asked to participate in a deeper way."