Key Takeaways
- • Fenwick & West LLP represented lead investor Lightspeed Venture Partners in a $350 million Series B financing round for Castelion, a defense technology company focused on conventional deterrence capabilities.
- • Altimeter Capital co-led the round alongside Lightspeed, with nine additional investors participating including Andreessen Horowitz, General Catalyst, First In, Space VC, BlueYard, Avenir, Champion Hill, Interlagos, Lavrock Ventures, and Cantos.
- • Castelion will deploy capital to expand U.S.-based manufacturing operations and workforce development, positioning the company for scale in the defense technology sector.
- • Fenwick's transaction team comprised 11 professionals across corporate, technology, privacy, regulatory, and antitrust practices, reflecting the deal's cross-functional complexity and regulatory scope.
Summary
Fenwick & West LLP served as legal counsel to Lightspeed Venture Partners in Castelion's $350 million Series B financing, announced December 5, 2025. Lightspeed led the investment round, with Altimeter Capital as co-lead investor. The transaction drew participation from a broad syndicate of venture capital firms, including top-tier names such as Andreessen Horowitz and General Catalyst, alongside emerging and specialized investors including Space VC, BlueYard, Avenir, Champion Hill, Interlagos, Lavrock Ventures, and Cantos.
Castelion operates in the defense technology sector with a stated focus on restoring American conventional deterrence capability. The company intends to deploy the $350 million in proceeds toward expansion of manufacturing capacity and workforce development infrastructure across the United States. This deployment strategy signals investor confidence in Castelion's operational scaling and reflects sector demand for domestic defense manufacturing capabilities.
The legal representation required substantial cross-functional expertise. Fenwick's transaction team was structured across multiple practice areas: corporate partners Michael Brown and Aaron Ginsburg led the engagement, supported by associates Teresa Anselmo and Josh Ellis. The deal also engaged Joseph Schenck (technology transactions partner) with associate Joanne Dynak; privacy counsel Melanie Jolson; regulatory partner Mark Ostrau with associates Andrew Martinez and Sofia Chalat; and antitrust partner Tom Ensign with counsel Meredith Mommers. This multidisciplinary composition reflects the complexity of venture-scale defense technology financing, particularly given regulatory and compliance considerations inherent to the sector.
Castelion operates in the defense technology sector with a stated focus on restoring American conventional deterrence capability. The company intends to deploy the $350 million in proceeds toward expansion of manufacturing capacity and workforce development infrastructure across the United States. This deployment strategy signals investor confidence in Castelion's operational scaling and reflects sector demand for domestic defense manufacturing capabilities.
The legal representation required substantial cross-functional expertise. Fenwick's transaction team was structured across multiple practice areas: corporate partners Michael Brown and Aaron Ginsburg led the engagement, supported by associates Teresa Anselmo and Josh Ellis. The deal also engaged Joseph Schenck (technology transactions partner) with associate Joanne Dynak; privacy counsel Melanie Jolson; regulatory partner Mark Ostrau with associates Andrew Martinez and Sofia Chalat; and antitrust partner Tom Ensign with counsel Meredith Mommers. This multidisciplinary composition reflects the complexity of venture-scale defense technology financing, particularly given regulatory and compliance considerations inherent to the sector.
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