<PAGE>

                                                                   EXHIBIT 10.13

                              SECOND AMENDMENT TO
                      THREE-YEAR REVOLVING CREDIT AGREEMENT

         THIS SECOND AMENDMENT, dated as of October 17, 2003 (this "Amendment"),
amends and modifies a certain Three-Year Revolving Credit Agreement, dated as of
June 14, 2002, as amended by an Amendment dated as of June 20, 2003 (as so
amended, the "Credit Agreement"), among ALLEGHANY CORPORATION (the "Borrower"),
the Banks named therein and U.S. BANK NATIONAL ASSOCIATION, as Agent for the
Banks (in such capacity, the "Agent"). Terms not otherwise expressly defined
herein shall have the meanings set forth in the Credit Agreement.

         FOR VALUE RECEIVED, the Borrower, the Banks which are signatories
hereto and the Agent agree as follows:

                  ARTICLE I - AMENDMENT TO THE CREDIT AGREEMENT

         Upon effectiveness of this Amendment as provided below, the Credit
Agreement shall be deemed to be amended as follows.

         1.1 Applicable Margin. The table in the definition of "Applicable
Margin" is amended to read as follows:

<TABLE>
<CAPTION>
                                          Applicable Margin
Level               Rating            (basis points per annum)
--------------------------------------------------------------
<S>            <C>                    <C>
 I             A/A2 or higher                   50.0
--------------------------------------------------------------
 II            A-/A3                            55.0
--------------------------------------------------------------
 III           BBB+/Baal                        67.5
--------------------------------------------------------------
 IV            BBB/Baa2                         80.0
--------------------------------------------------------------
 V             BBB-/Baa3                        92.5
--------------------------------------------------------------
 VI            BB+/Bal or lower                130.0
--------------------------------------------------------------
</TABLE>

In paragraph (a) of such definition, the parenthetical "(Level V being the
lowest Level)" is amended to read "(Level VI being the lowest Level)".

         1.2 Utilization Fee Rate. The table in the definition of "Utilization
Fee Rate" is amended to read as follows:

<TABLE>
<CAPTION>
                        Utilization Fee Rate
Level                 (basis points per annum)
----------------------------------------------
<S>                   <C>
 I                              0.0
----------------------------------------------
 II                            20.0
----------------------------------------------
 III                           32.5
----------------------------------------------
 IV                            45.0
----------------------------------------------
 V                             57.5
----------------------------------------------
 VI                            70.0
----------------------------------------------
</TABLE>

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         1.3 Revolving Commitment Fees. Section 2.9(1) is amended to read as
follows:

                  "2.9(a) The Borrower shall pay to the Agent, for the account
         of each Bank, fees (the "Revolving Commitment Fees") in an amount
         determined by applying to the average daily Unused Revolving Commitment
         of such Bank for the period from the Closing Date to the Termination
         Date a rate of (i) at any time that any of Levels I through V apply,
         0.25% per annum, or (b) at any time that Level VI applies, 0.375% per
         annum. Such Revolving Commitment Fees are payable in arrears quarterly
         on the last day of each calendar quarter and on the Termination Date."

         1.4 Unrestricted Liquid Assets. Section 6.15 is amended by deleting
"less than 1.25 to 1.00" and inserting "less than 1.10 to 1.00" in place
thereof. In the form of Compliance Certificate (Exhibit 5.1) the reference in
the corresponding Section to "Must be at least 1.25" is deleted and "Must be at
least 1.10" is inserted in place thereof.

         1.5 Disposition of Loans. The Second proviso of the second sentence of
Section 9.6 is deleted. Such proviso read, and the text deleted reads:

         "and provided further, that concurrently with the assignment of a
         portion of any Bank's Revolving Percentage hereunder, such Bank shall
         assign a like Revolving Percentage under the 364-Day Credit Agreement".

         1.6 Construction. All references in the Credit Agreement to "this
Agreement", "herein" and similar references shall be deemed to refer to the
Credit Agreement as amended by this Amendment and as may be further amended,
restated, supplemented or otherwise modified from time to time.

                   ARTICLE II - REPRESENTATIONS AND WARRANTIES

         To induce the Banks and the Agent to enter into this Amendment and to
make and maintain the Loans under the Credit Agreement as amended hereby, the
Borrower hereby warrants and represents to the Banks and the Agent that it is
duly authorized to execute and deliver this Amendment, and to perform its
obligations under the Credit Agreement as amended hereby, and that this
Amendment constitutes the legal, valid and binding obligations of the Borrower,
enforceable in accordance with its terms.

                       ARTICLE III - CONDITIONS PRECEDENT

         This Amendment shall become effective on the date first set forth
above, provided, however, that the effectiveness of this Amendment is subject to
the satisfaction of each of the following conditions precedent:

         3.1 Warranties. The representations and warranties in Article IV of the
Credit Agreement shall be true and correct as though made on the date hereof
(other than those which speak as of a specific date, which shall be true and
correct as of such date). The execution by the

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Borrower of this Amendment shall be deemed a representation that the Borrower
has complied with the foregoing condition.

         3.2 Defaults. Before and after giving effect to this Amendment, no
Default and no Event of Default shall have occurred and be continuing under the
Credit Agreement. The execution by the Borrower of this Amendment shall be
deemed a representation that the Borrower has complied with the foregoing
condition.

         3.3 Documents. The Company, each Bank and the Agent shall have executed
and delivered this Amendment.

                              ARTICLE IV - GENERAL

         4.1 Expenses. The Borrower agrees to reimburse the Agent upon demand
for all reasonable expenses (including reasonable attorneys' fees and legal
expenses) incurred by the Agent in connection with the preparation, negotiation
and execution of this Amendment and any other document required to be furnished
herewith, and in enforcing the obligations of the Borrower hereunder, and to pay
and save the Agent harmless from all liability for, any stamp or other taxes
which may be payable with respect to the execution or delivery of this
Amendment, which obligations of the Borrower shall survive any termination of
the Credit Agreement,

         4.2 Counterparts. This Amendment may be executed in as many
counterparts as may be deemed necessary or convenient, and by the different
parties hereto on separate counterparts, each of which, when so executed, shall
be deemed an original but all such counterparts shall constitute but one and the
same instrument.

         4.3 Severability. Any provision of this Amendment which is prohibited
or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining portions hereof or affecting the validity or
enforceability of such provisions in any other jurisdiction.

         4.4 Law. This Amendment shall be governed by the internal laws of the
State of Minnesota, without giving effect to conflict of laws principles
thereof, but giving effect to federal laws of the United States applicable to
national banks.

         4.5 Successors; Enforceability. This Amendment shall be binding upon
the Borrower, the Banks and the Agent and their respective successors and
assigns, and shall inure to the benefit of the Borrower, the Banks and the Agent
and the successors and assigns of the Banks and the Agent. Except as hereby
amended, the Credit Agreement shall remain in full force and effect and is
hereby ratified and confirmed in all respects.

                            (signature page follows)

<PAGE>

       IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their respective officers thereunto duly authorized as of the date
first written above.

                                      ALLEGHANY CORPORATION

                                      By: /s/ Peter R. Sismondo
                                         ----------------------------
                                      Title: VP

                                      U.S. BANK NATIONAL ASSOCIATION, as
                                      Agent and as a Bank

                                      By: /s/ Sam S. Pepper
                                         ----------------------------
                                      Title: Vice President

                                      LaSALLE BANK NATIONAL
                                      ASSOCIATION, as a Bank

                                      By: /s/ James J. Hess
                                         ----------------------------
                                             James J. Hess
                                      Title: First Vice President

                                      M&I MARSHALL & ILSLEY BANK,
                                      as a Bank

                                      By: /s/ Jeffrey T. Ticknor
                                         ----------------------------
                                      Title: Sr. Vice President
                                      and

                                      By: /s/ John Ronzia
                                         ----------------------------
                                      Title: Vice President

                                      THE BANK OF NOVA SCOTIA, as a Bank

                                      By: /s/ John Campbell
                                         ----------------------------
                                         By: John Campbell
                                      Title: Managing Director

                                      BANK HAPOALIM B.M., as a Bank

                                      By: /s/ James P. Surless
                                         ----------------------------
                                      Title: VP
                                      and

                                      By: /s/ Laura A. Raffa
                                         ----------------------------
                                      Title: SVP