Exhibit 10.1

FIRST AMENDMENT TO CREDIT AGREEMENT
($400,000,000 UNSECURED SENIOR REVOLVING CREDIT FACILITY)

This FIRST AMENDMENT TO CREDIT AGREEMENT (this “First Amendment”), is dated as
of February 25, 2010, and entered into by and among ALLIED WORLD ASSURANCE
COMPANY HOLDINGS, LTD, an exempted company incorporated in Bermuda (“Holdings”),
ALLIED WORLD ASSURANCE COMPANY, LTD, an exempted company incorporated in Bermuda
(“Allied World,” and together with Holdings, the “Borrowers”), the Lenders party
hereto, and WACHOVIA BANK, NATIONAL ASSOCIATION (“Wachovia”), as Administrative
Agent, L/C Agent and Fronting Bank for the Lenders.

RECITALS

A. The Borrowers, the several lenders from time to time parties thereto (the
“Lenders”), the Administrative Agent and Bank of America, N.A., as Syndication
Agent, are party to the Credit Agreement dated as of November 27, 2007 (as
amended, supplemented, restated and modified from time to time, the “Unsecured
Credit Agreement”). Capitalized terms used herein without definition shall have
the meanings given to them in the Unsecured Credit Agreement.

B. The Borrowers have requested certain amendments to the Unsecured Credit
Agreement and the Administrative Agent and the Required Lenders have agreed to
make such amendments on the terms and conditions set forth herein.

STATEMENT OF AGREEMENT

NOW, THEREFORE, in consideration of the foregoing and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto agree as follows:

ARTICLE I
AMENDMENTS TO CREDIT AGREEMENT

1.1 Amendments to Section 1.1 (Defined Terms).

(a) The following definitions are hereby added to Section 1.1 of the Unsecured
Credit Agreement in appropriate alphabetical order:

“Designated Lender” means any Lender that is either a Defaulting Lender or a
Downgraded Lender.

“Downgraded Lender” means any Lender that has a non-credit enhanced senior
unsecured debt rating below A- or A3 from S&P or Moody’s, respectively.

“First Amendment” shall mean the First Amendment to Credit Agreement, dated as
of February 25, 2010, among the Borrowers, the Lenders party thereto, and the
Administrative Agent.

“First Amendment Effective Date” shall mean the date upon which the conditions
to the effectiveness of the First Amendment set forth in Article II thereof are
satisfied or waived in accordance with their terms.

“Net Termination Obligations” means, in respect of any one or more Hedge
Agreements, after taking into account the effect of any legally enforceable
netting agreement relating to such Hedge Agreements, (a) for any date on or
after the date such Hedge Agreement have been closed out and termination
obligations(s) determined in accordance therewith, such termination
obligation(s), and (b) for any date prior to the date referenced in clause (a),
the amount(s) determined as the mark-to-market value(s) for such Hedge
Agreements, as determined based upon one or more mid-market or other readily
available quotations provided by any recognized dealer in such Hedge Agreements,
reputable pricing agent or custodian bank (which may include a Lender or any
Affiliate of a Lender).

(b) The following definitions in Section 1.1 of the Unsecured Credit Agreement
are hereby amended and restated in their entirety as follows:

“Base Rate” means the highest of (i) the per annum interest rate publicly
announced from time to time by Wachovia in Charlotte, North Carolina, to be its
prime rate (which may not necessarily be its lowest or best lending rate), as
adjusted to conform to changes as of the opening of business on the date of any
such change in such prime rate, (ii) the Federal Funds Rate plus 0.5% per annum,
as adjusted to conform to changes as of the opening of business on the date of
any such change in the Federal Funds Rate and (iii) the LIBOR Rate for an
interest period of one month plus 1.00%.

“Defaulting Lender” means any Lender that (i) has refused to fund, or otherwise
defaulted in the funding of, its Ratable Share of (A) any Borrowing requested
and permitted be made hereunder, (B) any drawing made on any Syndicated Letter
of Credit or (C) any participation interest in any Participated Letter of Credit
in accordance with the terms hereof, (ii) has notified the Borrowers, the
Administrative Agent, an Issuing Bank or any Fronting Bank in writing that it
does not intend to comply with any or all of its funding obligations under this
Agreement or has made a public statement to the effect that it does not intend
to comply with any or all of its funding obligations under this Agreement or
generally under other agreements in which it commits to extend credit, (iii) has
failed, within three Business Days after receipt of a written request from the
Administrative Agent to confirm that it will comply with the terms of this
Agreement relating to its obligation to fund prospective Loans, drawings on or
participations in Letters of Credit, (iv) has failed to pay to the
Administrative Agent, any Fronting Bank or any Lender when due an amount owed by
such Lender pursuant to the terms of this Agreement, unless such amount is
subject to a good faith dispute, or (v) (a) has been deemed, become or is
insolvent or is the Subsidiary of a Person that has been deemed, become or is
insolvent or (b) has become the subject of a proceeding under the Bankruptcy
Code or under any other applicable Debtor Relief Laws, or has had a receiver,
conservator, trustee, custodian or similar official appointed for it or any
substantial part of its property, or has taken any action in furtherance of, or
indicating its consent to, approval of or acquiescence in any such proceeding or
appointment or is a Subsidiary of a Person that has become the subject of a
proceeding under the Bankruptcy Code or under any other applicable Debtor Relief
Laws, or has had a receiver, conservator, trustee, custodian or similar official
appointed for it or any substantial part of its property, or has taken any
action in furtherance of, or indicating its consent to, approval of or
acquiescence in any such proceeding or appointment.

“Hedge Agreement” means any interest rate, credit default or foreign currency
rate swap, future, cap, collar, hedge, forward rate or other similar agreement
or arrangement (including any option to enter into any of the foregoing)
designed to protect against fluctuations in interest rates, credit spreads or
currency exchange rates.

(c) Clause (x) in the definition of “Indebtedness” is hereby amended and
restated in its entirety as follows:

“(x) the Net Termination Obligations of such Person under any Hedge Agreements,”

1.2 Amendments to Section 3.3 (Conditions Precedent to the Issuance of Letters
of Credit). Section 3.3(ix) is hereby amended and restated in its entirety as
follows:

“(ix) with respect to the issuance of a Participated Letter of Credit or the
fronting for a Non-NAIC Lender in respect of a Syndicated Letter of Credit
pursuant to Section 3.1(h), a default of any Lender’s obligations to fund under
Section 3.2(e) exists or any Lender is at such time a Designated Lender, unless
the applicable Fronting Bank has entered into satisfactory arrangements with the
Borrowers or such Lender to eliminate the applicable Fronting Bank’s risk with
respect to such Lender.”

1.3 Amendments to Section 8.1 (Fundamental Changes). Section 8.1 is hereby
amended and restated in its entirety as follows:

“Section 8.1 Fundamental Changes. Except as permitted under Section 8.4, such
Borrower will not, and will not permit or cause any of its Subsidiaries to,
liquidate, wind up or dissolve, or enter into any consolidation, merger or other
combination, or agree to do any of the foregoing; provided, however, (i) that
any such Borrower or any Subsidiary may merge into or consolidate with any other
Person so long as (y) the surviving corporation is a Borrower or a Wholly Owned
Subsidiary of any Borrower (and in any event, if any Borrower is a party to such
merger or consolidation, the surviving corporation shall be a Borrower, it being
understood and agreed that in the case of a merger or consolidation between a
Subsidiary of Holdings with Holdings, the survivor corporation of such merger or
consolidation shall be Holdings), and (z) immediately after giving effect
thereto, no Default or Event of Default would occur or exist and (ii) any
Subsidiary may liquidate, wind up or dissolve if (x) such Subsidiary owns no
more than a nominal amount of assets, has no more than a nominal amount of
liabilities and does not actively conduct, transact or otherwise engage in any
business or operations and (y) such liquidation, winding up or dissolution is
not materially disadvantageous to the Lenders.”

1.4 Amendment to Section 8.2 (Indebtedness). Clause (viii) of Section 8.2 of the
Unsecured Credit Agreement is hereby amended and restated in its entirety as
follows:

“(viii) obligations (contingent or otherwise) existing or arising under any
Hedge Agreement entered into by such Person in the ordinary course of business
for the purpose of protecting against fluctuations in interest rates, credit
spreads or currency exchange rates and not for purposes of speculation or taking
a ‘market view’;”

1.5 Amendments to Section 8.3 (Liens). Section 8.3 of the Unsecured Credit
Agreement is hereby amended by deleting the word “and” at the conclusion of
clause (v) and substituting therefor a comma, renumbering the existing clause
(vi) as clause (vii), and adding a new clause (vi) to read as follows:

“(vi) Liens on cash or other investment assets not at any time exceeding
$265,000,000 securing Indebtedness permitted under Section 8.2(viii); and”

1.6 Amendments to Section 9.1 (Events of Default). Section 9.1(e) of the
Unsecured Credit Agreement is hereby amended by deleting the words “net
termination obligation” in clause (z) therein and substituting therefor the
words “Net Termination Obligation”.

ARTICLE II
CONDITIONS OF EFFECTIVENESS

This First Amendment shall become effective as of the date (the “First Amendment
Effective Date”) when, and only when, each of the following conditions precedent
shall have been satisfied:

(a) The Administrative Agent shall have received, dated as of the First
Amendment Effective Date, an executed counterpart hereof from each of the
Borrowers and the Required Lenders;

(b) On the First Amendment Effective Date, the representations and warranties
set forth in Article III hereof shall be true and correct; and

(c) The Borrowers shall have paid all reasonable out-of-pocket costs and
expenses of the Administrative Agent in connection with the preparation,
negotiation, execution and delivery of this First Amendment (including, without
limitation, the reasonable fees and out-of-pocket expenses of counsel for the
Administrative Agent with respect thereto).

ARTICLE III
REPRESENTATIONS AND WARRANTIES

Each Borrower hereby represents and warrants, on and as of the First Amendment
Effective Date, that (i) the representations and warranties contained in the
Unsecured Credit Agreement and the other Credit Documents qualified as to
materiality are true and correct and those not so qualified are true and correct
in all material respects, both immediately before and after giving effect to
this First Amendment (except to the extent any such representation or warranty
is expressly stated to have been made as of a specific date, in which case such
representation or warranty is true and correct (if qualified as to materiality)
or true and correct in all material respects (if not so qualified), in each case
only on and as of such specific date), (ii) this First Amendment has been duly
authorized, executed and delivered by such Borrower and constitutes the legal,
valid and binding obligation of such Borrower enforceable against it in
accordance with its terms and (iii) no Default or Event of Default shall have
occurred and be continuing on the First Amendment Effective Date, both
immediately before and after giving effect to the First Amendment.

ARTICLE IV
ACKNOWLEDGEMENT AND CONFIRMATION

Each party to this First Amendment hereby confirms and agrees that, after giving
effect to this First Amendment, and except as expressly amended hereby, the
Unsecured Credit Agreement and the other Credit Documents to which it is a party
remain in full force and effect and enforceable against such party in accordance
with their respective terms and shall not be discharged, diminished, limited or
otherwise affected in any respect. Each Borrower represents and warrants to the
Lenders that as of the First Amendment Effective Date it has no knowledge of any
claims, counterclaims, offsets, or defenses to or with respect to its
obligations under the Credit Documents, or if such Borrower has any such claims,
counterclaims, offsets, or defenses to the Credit Documents or any transaction
related to the Credit Documents, the same are hereby waived, relinquished, and
released in consideration of the execution of this First Amendment. This
acknowledgement and confirmation by each Borrower is made and delivered to
induce the Administrative Agent and the Lenders to enter into this First
Amendment, and each Borrower acknowledges that the Administrative Agent and the
Lenders would not enter into this First Amendment in the absence of the
acknowledgement and confirmation contained herein.

ARTICLE V
MISCELLANEOUS

5.1 Governing Law. This First Amendment shall be governed by and construed and
enforced in accordance with the laws of the State of New York (including
Sections 5-1401 and 5-1402 of the New York General Obligations Law, but
excluding all other choice of law and conflicts of law rules).

5.2 Credit Document. As used in the Unsecured Credit Agreement, “hereinafter,”
“hereto,” “hereof,” and words of similar import shall, unless the context
otherwise requires, mean the Unsecured Credit Agreement after amendment by this
First Amendment. Any reference to the Unsecured Credit Agreement or any of the
other Credit Documents herein or in any such documents shall refer to the
Unsecured Credit Agreement and Credit Documents as amended hereby. This First
Amendment is limited to the matters expressly set forth herein, and shall not
constitute or be deemed to constitute an amendment, modification or waiver of
any provision of the Unsecured Credit Agreement except as expressly set forth
herein. This First Amendment shall constitute a Credit Document under the terms
of the Unsecured Credit Agreement.

5.3 Expenses. The Borrowers shall (i) pay all reasonable fees and expenses of
counsel to the Administrative Agent, and (ii) reimburse the Administrative Agent
for all reasonable out-of-pocket costs and expenses, in each case, in connection
with the preparation, negotiation, execution and delivery of this First
Amendment and the other Credit Documents delivered in connection herewith.

5.4 Severability. To the extent any provision of this First Amendment is
prohibited by or invalid under the applicable law of any jurisdiction, such
provision shall be ineffective only to the extent of such prohibition or
invalidity and only in any such jurisdiction, without prohibiting or
invalidating such provision in any other jurisdiction or the remaining
provisions of this First Amendment in any jurisdiction.

5.5 Successors and Assigns. This First Amendment shall be binding upon, inure to
the benefit of and be enforceable by the respective successors and permitted
assigns of the parties hereto.

5.6 Construction. The headings of the various sections and subsections of this
First Amendment have been inserted for convenience only and shall not in any way
affect the meaning or construction of any of the provisions hereof.

5.7 Counterparts; Integration. This First Amendment may be executed and
delivered via facsimile or electronic mail with the same force and effect as if
an original were executed and may be signed in any number of counterparts, each
of which shall be an original, with the same effect as if the signatures hereto
were upon the same instrument. This First Amendment constitutes the entire
contract among the parties hereto with respect to the subject matter hereof and
supersedes any and all prior agreements and understandings, oral or written,
relating to the subject matter hereof.

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

ALLIED WORLD ASSURANCE COMPANY HOLDINGS, LTD

     
By:
Name:
Title:
  /s/ Joan H. Dillard
Joan H. Dillard
E.V.P. and Chief Financial Officer
 
   
By:
Name:
Title:
  /s/ Marchelle D. Lewis
Marchelle Lewis
V.P. and Treasurer
 
   

    ALLIED WORLD ASSURANCE COMPANY, LTD

     
By:
Name:
Title:
  /s/ Joan H. Dillard
Joan H. Dillard
E.V.P. and Chief Financial Officer
 
   
By:
Name:
Title:
  /s/ Marchelle D. Lewis
Marchelle Lewis
V.P. and Treasurer
 
   

   

LENDERS: WACHOVIA BANK, NATIONAL

ASSOCIATION, as the Administrative Agent, the L/C Agent, a Fronting Bank and as
a Lender

By: /s/ William R. Goley
Name: Willian R. Goley
Title: Director

Wachovia Bank , National Association

      JPMORGAN CHASE BANK, N.A.

By: /s/ Melvin D. Jackson
Name: Melvin D. Jackson
Title: V.P.

SUNTRUST BANK

By: /s/ William Christensen
Name: William Christensen
Title: Director

Credit Agricole Corporate & Investment Bank

By: /s/ Charlie Kornberger
Name: Charlie Kornberger
Title: Managing Director

By: /s/ Gina Harth-Cryde
Name: Gina Harth-Cryde
Title: Managing Director

ING BANK N.V., LONDON BRANCH

By: /s/ N J Marchant
Name: N J Marchant
Title: Director

By: /s/ M E R Sherman
Name: M E R Sherman
Title: Managing Director

Bank of America, N.A.

By: /s/ Brady Fife
Name: Brady Fife
Title: Director

BARCLAYS BANK PLC

By: /s/ Nicholas A. Bell
Name: Nicholas A. Bell
Title: Director

Lloyds TSB Bank plc

By: /s/ Morgan Beanland
Name: Morgan Beanland
Title: SVP FI B033

By: /s/ Shane Klein
Name: Shane Klein
Title: SVP FI K042

The Governor and Company of the Bank of Ireland, as Lender

By: /s/ K Rockett /s/ A Donovan
Name: K Rockett            A Donovan
Title: Senior Manager Manager

The Bank of N.T. Butterfield & Son Limited

By: /s/ Alan Day
Name: Alan Day
Title: Vice President

By: /s/ Curtis Ballantyne
Name: Curtis Ballantyne
Title: Senior Vice President