SCHEDULE 13D/A 0001142206 XXXXXXXX LIVE 2 Common stock, par value $0.20 per share 02/05/2026 false 0000011544 084423102 W. R. Berkley Corporation

475 Steamboat Road Greenwich CT 06830

Mitsui Sumitomo Insurance Co. 81-3-3259-1462 Ltd., Attn: Kunihisa Kawasaki 9, Kanda-Surugadai, 3-chome, Chiyoda-Ku Tokyo M0 101-8011 Debevoise & Plimpton LLP (212) 909-6000 Attn: Eric T. Juergens, Esq 66 Hudson Boulevard New York NY 10001 0001142206 N Mitsui Sumitomo Insurance Co., Ltd. b WC N M0 56458656 0 56458656 0 56458656 Y 14.9 IC The aggregate amount in row (11) does not reflect shares of common stock, par value $0.20 per share (the "Common Stock"), of W. R. Berkley Corporation (the "Issuer") held by WR Berkley & Others LLC ("Family Holdings"), as further described in Items 5(a) and 6. Percentages are based on 380,021,174 shares of Common Stock outstanding as of October 28, 2025, as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on November 3, 2025. 0001431048 N MS&AD Insurance Group Holdings, Inc. b WC N M0 0 56458656 0 56458656 56458656 Y 14.9 HC The aggregate amount in row (11) does not reflect shares of Common Stock held by Family Holdings, as further described in Items 5(a) and 6. Percentages are based on 380,021,174 shares of Common Stock outstanding as of October 28, 2025, as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on November 3, 2025. Common stock, par value $0.20 per share W. R. Berkley Corporation 475 Steamboat Road Greenwich CT 06830 This Amendment No. 2 amends the Statement on Schedule 13D initially filed on December 11, 2025 with the Securities and Exchange Commission, and amended on January 14, 2026 (as amended, the "Statement") by MS&AD Insurance Group Holdings, Inc., a kabushiki kaisha (stock corporation) organized under the laws of Japan ("MS&AD Holdings"), and Mitsui Sumitomo Insurance Co., Ltd., a kabushiki kaisha (stock corporation) organized under the laws of Japan ("MSI" and together with MS&AD Holdings, the "Reporting Persons"). Item 3 is hereby amended and supplemented by adding the following paragraph at the end of Item 3: Between January 15, 2026 and February 6, 2026, MSI purchased an aggregate of 3,732,152 shares of Common Stock in the open market at average prices per share as set forth in Schedule I to this Statement for an aggregate purchase price of $252,827,490.60, all of which was paid using cash on hand. The shares of Common Stock were purchased in the open market pursuant to the previously disclosed 10b5-1 purchase plan entered into with Jefferies LLC on October 3, 2025. Item 5 is hereby amended and restated in its entirety to read as follows: MSI beneficially owns 56,458,656 shares of Common Stock, representing fourteen and nine-tenths percent (14.9%) of the shares of Common Stock outstanding. Because MSI is its wholly-owned subsidiary, MS&AD Holdings may, in accordance with the rules of the Securities and Exchange Commission, be deemed to be an indirect beneficial owner of the shares of Common Stock beneficially owned by MSI. MS&AD Holdings disclaims beneficial ownership of such shares. The percentage beneficial ownership of the Reporting Persons has been determined based on 380,021,174 shares of Common Stock outstanding as of October 28, 2025, as reported in the Issuer's Form 10-Q filed with the Securities and Exchange Commission on November 3, 2025. The beneficial ownership information set forth above does not include any securities of the Issuer beneficially owned by Family Holdings. As a result of the Framework Agreement and LLC Agreement described in Item 6 of this Statement, the Reporting Persons may be deemed to beneficially own and share voting power over the shares of Common Stock beneficially owned by Family Holdings. As of the date hereof, Family Holdings beneficially owns an aggregate of 67,069,033 shares of Common Stock (approximately seventeen and six-tenths percent (17.6%) of the total number of shares of Common Stock outstanding). This Statement is not an admission or acknowledgment that the Reporting Persons constitute a "group" within the meaning of Rule 13d-5(b)(1) under the Act with Family Holdings. In addition to the description set forth above in Item 5(a), see the cover pages of this Statement for indications of the respective voting powers and disposition powers of the Reporting Persons. Schedule I sets forth the purchases of shares of Common Stock by MSI in the open market between January 15, 2026 and February 6, 2026 and is incorporated herein by reference. Except for the foregoing or as otherwise set forth herein, each of the Reporting Persons reports that neither it, nor to its knowledge, any other person named in Item 2 of this Statement, has effected any transactions in Common Stock during the past 60 days. Except as set forth herein, no one other than the Reporting Persons has the right to receive, or the power to direct the receipt of, dividends from, or the proceeds from the sale of, any of the securities of the Issuer beneficially owned by the Reporting Persons as described in this Item 5. Not applicable. 99.8 Schedule I, dated February 6, 2026 99.9 Joint Filing Agreement, dated December 11, 2025, by and between Mitsui Sumitomo Insurance Co., Ltd. and MS&AD Insurance Group Holdings, Inc. (incorporated by reference to Exhibit 99.1 to the Schedule 13D filed by the Reporting Persons with the SEC on December 11, 2025) Mitsui Sumitomo Insurance Co., Ltd. /s/ Hironori Morimoto 02/06/2026 MS&AD Insurance Group Holdings, Inc. /s/ Hironori Morimoto 02/06/2026