Mitsui Sumitomo lifts W. R. Berkley (NYSE: WRB) stake to 13.9%

Rhea-AI Filing Summary

Mitsui Sumitomo Insurance Co., Ltd. and MS&AD Insurance Group Holdings, Inc. have updated their ownership disclosure for W. R. Berkley Corporation. Mitsui Sumitomo purchased 4,124,916 shares of common stock in the open market between December 18, 2025 and January 14, 2026 for an aggregate $287,433,279.73, funded with cash on hand under a previously disclosed 10b5-1 purchase plan with Jefferies LLC.

Following these transactions, Mitsui Sumitomo beneficially owns 52,726,504 shares of W. R. Berkley common stock, representing 13.9% of the 380,021,174 shares outstanding as of October 28, 2025. As Mitsui Sumitomo is a wholly owned subsidiary, MS&AD Insurance Group Holdings may be deemed an indirect beneficial owner of these shares but disclaims beneficial ownership. The filing also notes that WR Berkley & Others LLC 17.6% of the outstanding shares, which the reporting persons may be deemed to share voting power over under certain agreements, while not admitting they form a group.

Insights

Equity ownership and governance analyst

Large strategic holder lifts W. R. Berkley stake to 13.9% via planned open-market buying.

Mitsui Sumitomo Insurance Co., Ltd. reports open-market purchases of 4,124,916 W. R. Berkley common shares between December 18, 2025 and January 14, 2026 for an aggregate $287,433,279.73, funded with cash on hand under a 10b5-1 plan with Jefferies LLC. These purchases raise its beneficial holdings to 52,726,504 shares, or 13.9% of the 380,021,174 shares outstanding as of October 28, 2025.

Because Mitsui Sumitomo is wholly owned by MS&AD Insurance Group Holdings, Inc., MS&AD may be deemed an indirect beneficial owner under SEC rules, though it expressly disclaims beneficial ownership. Separately, WR Berkley & Others LLC 17.6% of the outstanding stock, and the reporting persons may be deemed to share voting power over those shares under a Framework Agreement and LLC Agreement described in Item 6.

The statement emphasizes that this is not an admission that the reporting persons and Family Holdings constitute a “group” under Rule 13d‑5(b)(1). Future company filings describing the referenced agreements and any further Schedule 13D amendments will clarify how these ownership and voting relationships evolve over time.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

W. R. BERKLEY CORPORATION

(Name of Issuer)

Common Stock, par value $0.20 per share

(Title of Class of Securities)

084423102

(CUSIP Number)

Mitsui Sumitomo Insurance Co.
Attn: Kunihisa Kawasaki, 9, Kanda-Surugadai, 3-chome, Chiyoda-Ku
Tokyo, M0, 101-8011
81-3-3259-1462

Debevoise & Plimpton LLP
Attn: Eric T. Juergens, Esq, 66 Hudson Boulevard
New York, NY, 10001
(212) 909-6000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

01/13/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 084423102

1

Name of reporting person

Mitsui Sumitomo Insurance Co., Ltd.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

JAPAN

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 52,726,504.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 52,726,504.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

52,726,504.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

13.9 %

14

Type of Reporting Person (See Instructions)

IC

Comment for Type of Reporting Person:

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.

SCHEDULE 13D

CUSIP No. 084423102

1

Name of reporting person

MS&AD Insurance Group Holdings, Inc.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

JAPAN

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 52,726,504.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 52,726,504.00

11

Aggregate amount beneficially owned by each reporting person

52,726,504.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

13.9 %

14

Type of Reporting Person (See Instructions)

HC

Comment for Type of Reporting Person:

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.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.20 per share
(b)	Name of Issuer: W. R. BERKLEY CORPORATION
(c)	Address of Issuer's Principal Executive Offices: 475 STEAMBOAT ROAD, GREENWICH, CONNECTICUT , 06830.
Item 1 Comment: This Amendment No. 1 amends the Statement on Schedule 13D initially filed on December 11, 2025 with the Securities and Exchange Commission (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.	Source and Amount of Funds or Other Consideration
	Item 3 is hereby amended and supplemented by adding the following paragraph at the end of Item 3: Between December 18, 2025 and January 14, 2026, MSI purchased an aggregate of 4,124,916 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 $287,433,279.73, 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.	Interest in Securities of the Issuer
(a)	Item 5 is hereby amended and restated in its entirety to read as follows: MSI beneficially owns 52,726,504 shares of Common Stock, representing thirteen and nine tenths percent (13.9%) 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.
(b)	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.
(c)	Schedule I sets forth the purchases of shares of Common Stock by MSI in the open market between December 18, 2025 and January 14, 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.
(d)	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.
(e)	Not applicable.
Item 7.	Material to be Filed as Exhibits.
	99.6 Schedule I, dated January 14, 2026 99.7 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)

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Mitsui Sumitomo Insurance Co., Ltd.

Signature:	/s/ Hironori Morimoto
Name/Title:	Hironori Morimoto/Authorized Signatory
Date:	01/14/2026

MS&AD Insurance Group Holdings, Inc.

Signature:	/s/ Hironori Morimoto
Name/Title:	Hironori Morimoto/Authorized Signatory
Date:	01/14/2026

FAQ

How many W. R. Berkley (WRB) shares does Mitsui Sumitomo now beneficially own?

Mitsui Sumitomo Insurance Co., Ltd. now beneficially owns 52,726,504 shares of W. R. Berkley common stock, representing 13.9% of the 380,021,174 shares outstanding as of October 28, 2025.

What recent share purchases in W. R. Berkley (WRB) did Mitsui Sumitomo make?

Between December 18, 2025 and January 14, 2026, Mitsui Sumitomo purchased an aggregate 4,124,916 shares of W. R. Berkley common stock in the open market for a total of $287,433,279.73, using cash on hand.

Was Mitsui Sumitomo’s increase in W. R. Berkley (WRB) shares under a trading plan?

Yes. The purchases were made pursuant to a previously disclosed Rule 10b5-1 purchase plan entered into with Jefferies LLC on October 3, 2025.

How is MS&AD Insurance Group Holdings related to Mitsui Sumitomo’s W. R. Berkley stake?

MS&AD Insurance Group Holdings, Inc. is the parent and wholly owns Mitsui Sumitomo. Under SEC rules it may be deemed an indirect beneficial owner of the 52,726,504 shares, but it disclaims beneficial ownership of those shares.

What stake in W. R. Berkley (WRB) does Family Holdings own according to the filing?

WR Berkley & Others LLC (Family Holdings) beneficially owns 67,069,033 shares of W. R. Berkley common stock, which is approximately 17.6% of the total shares outstanding as of October 28, 2025.

Do Mitsui Sumitomo, MS&AD, and Family Holdings form a group in W. R. Berkley (WRB)?

The filing states that, due to a Framework Agreement and LLC Agreement, the reporting persons may be deemed to beneficially own and share voting power over shares held by Family Holdings, but it also states that this is not an admission that they constitute a “group” under Rule 13d‑5(b)(1).