International Business Machines Corp. announced Sunday its $33.4 billion purchase of open source software company Red Hat Inc. The megadeal, which could change the face of cloud computing, is the largest ever acquisition of a software company and the third-largest ever in the technology sector, according to news reports.

Aside from its size and scope, the tie-up between IBM and Red Hat also has M&A lawyers talking about the outside legal advisers retained to pull off the deal, which both companies do not expect to be completed until the latter half of 2019.

Paul, Weiss, Rifkind, Wharton & Garrison is serving as lead M&A and finance counsel to IBM, while Hogan Lovells is advising the Armonk, New York-based technology giant on antitrust matters. Raleigh, North Carolina-based Red Hat has turned to Skadden, Arps, Slate, Meagher & Flom and Debevoise & Plimpton is representing Guggenheim Partners LLC and Morgan Stanley & Co. LLC in their roles as financial adviser to the target. Securities filings show that Simpson Thacher & Bartlett is working on financing for the deal arranged by JPMorgan Chase & Co. and The Goldman Sachs Group Inc.

Absent from that list of legal advisers is Cravath, Swaine & Moore, which has long served as outside counsel to IBM on a variety of notable engagements. A Cravath spokeswoman did not return a request for the names of any lawyers from the firm working on the deal, which is the largest in IBM's history. A source familiar with the IBM-Red Hat transaction told The American Lawyer that Cravath did not work on the matter.

Instead, IBM turned to a Paul Weiss team led by Scott Barshay, global head of the firm's M&A practice, corporate partner Steven Williams and partner Gregory Ezring, co-head of the firm's finance practice. Ezring, who joined Paul Weiss in 2011 from O'Melveny & Myers, where he co-chaired the latter's corporate finance and capital markets practice, has taken the lead for IBM on the financing for its Red Hat acquisition.

Barshay was one of the most high-profile lateral partner hires in recent memory when Paul Weiss recruited him from Cravath in 2016. At Cravath, Barshay spent more than 20 years advising on IBM deals and was part of the firm's strong relationship with the company.

In 2013 alone, Cravath advised IBM on its $2 billion buy of cloud computing company SoftLayer Technologies Inc. and $1 billion acquisition of Israeli fraud protection and security software provider Trusteer Ltd. As for Barshay, he handled IBM's $1.3 billion purchase of human resources software provider Kenexa Corp. in 2012, a $1.2 billion buy of software analytics maker SPSS Inc. in 2009, and a $1.7 billion acquisition of data analytics company Netezza Corp. and $5 billion merger with Canadian business intelligence firm Cognos Inc. in 2008.

In early 2013, Cravath solidified its ties to IBM by making a rare external partner hire in David Kappos, an intellectual property expert who spent more than 25 years as an in-house lawyer at IBM prior to serving as director of the U.S. Patent and Trademark Office. IBM's large in-house legal department, which for eight years was led by general counsel Robert Weber until his retirement in 2015, is now helmed by Weber's protégé, current legal chief Michelle Browdy. (Weber spoke with ALM in 2013 about his favorite law firms and pet peeves with outside counsel.)

Paul Weiss' big bet on Barshay yielded an immediate new client two years ago this month in Qualcomm Inc., which retained him and the firm to handle its ultimately ill-fated $47 billion acquisition of NXP Semiconductors NV. Qualcomm turned to Barshay and Paul Weiss again in late 2017 to advise on a $103 billion takeover offer from rival Broadcom Corp., a deal that collapsed earlier this year in the face of U.S. regulatory opposition. (Chinese regulators helped scuttle Qualcomm's NXP deal.)

Amid the Qualcomm deal drama, Barshay has stayed busy. He led a Paul Weiss team representing Kraft Heinz Food Co. on a $143 billion takeover bid for London-based Unilever plc, although that offer was subsequently withdrawn. In January of this year, Paul Weiss and Barshay were hired by Bioverativ Inc. to handle the drug maker's $11.6 billion sale to French pharmaceutical giant Sanofi SA. Bioverative was being spun off from parent company Biogen Inc., a Cravath client.

Paul Weiss' role for IBM on the Red Hat deal is the first major engagement for the firm by the company since Barshay came aboard two years ago. In late 2016, IBM turned to Cravath to handle its purchase for an undisclosed sum of Promontory Financial Group, which it acquired to bolster its Watson artificial intelligence platform. The PFG deal took place a little more than a month after Paul Weiss hired a prominent antitrust team from Cadwalader, Wickersham & Taft led by partner Charles “Rick” Rule.

While at Cadwalader, Rule served as antitrust counsel to Microsoft Corp. on its $26.2 billion acquisition of LinkedIn Corp. in 2016. That deal had been one of the largest in technology sector transaction history—topped only by Dell Inc.'s $67 billion buy of EMC Corp. in 2016 and Avago Technologies' $37 billion acquisition of Broadcom the year before—prior to IBM's deal with Red Hat this week. Rule's antitrust team is not currently advising IBM, leaving Paul Weiss just short of a capturing all of the outside legal work on a deal that should generate millions in attorney fees for the firm.

Hogan Lovells has picked up the antitrust work for IBM on the Red Hat deal via a cross-border team led by partners Logan Breed, Ciara Kennedy-Loest and Rachel Brandenburger. While Cravath has also had a long history of handling antitrust matters for IBM, several years ago Hogan Lovells became a lead external legal adviser on global competition issues for the company.

Hogan Lovells worked with Cravath in 2014 on the $2.3 billion sale of IBM's low-end server division to China's Lenovo Group Ltd. and $1.5 billion acquisition that same year of a semiconductor business owned by Globalfoundries Inc. In 2012, Hogan Lovells hired partner Harriet Pearson, a former chief privacy officer at IBM.

Skadden partner Howard Ellin, a veteran deal-maker and former global co-chair of corporate transactions at the firm, and fellow corporate partner Brandon Van Dyke are leading a team of lawyers advising Red Hat on its proposed sale to IBM. (The American Lawyer named Van Dyke one of its Dealmakers of the Year in 2016 for his role representing chemical giant E.I. du Pont de Nemours & Co. in a proxy battle with Nelson Peltz's Trian Fund Management LP; Ellin is the older brother of Hollywood screenwriter and producer Doug Ellin.)

Other Skadden lawyers working on the deal for Red Hat include executive compensation and benefits partner Regina Olshan; antitrust partners Clifford Aronson and Frederic Depoortere; banking partner Stephanie Teicher; tax partners David Rievman and Gavin White; IP and technology partner Stuart Levi; labor and employment partner David Schwartz; and benefits counsel Timothy Nelson.

Michael Cunningham, a former associate general counsel at IBM in London, has spent the past 14 years as general counsel for Red Hat. DeLisa Alexander, a former assistant general counsel at Red Hat, now serves as chief people officer for the company.

Debevoise corporate chair Jeffrey Rosen, another top M&A lawyer and former American Lawyer Dealmaker of the Year, and firm M&A co-head William Regner are advising Guggenheim and Morgan Stanley in their role as financial advisers for Red Hat. Debevoise litigation partner Daniel Abuhoff and counsel Erica Weisgerber are also advising the two financial advisers.

As for Paul Weiss, other lawyers working with Barshay, Ezring and Williams in representing IBM on the Red Hat deal include corporate partner John Kennedy; employee benefits partner Lawrence Witdorchic; finance partner Manuel Frey; tax partners Jeffrey Samuels and Scott Sontag; IP partner Claudine Meredith-Goujon; and counsel Jonathan Ashtor, Jarrett Hoffman, Caith Kushner, Frances Mi and Kyle Seifried.

Gregory Bomberger, an associate general counsel at IBM, has taken the in-house lead for the company on its bid for Red Hat, according to securities filings.