SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13D (RULE 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13D-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13D-2(a) (AMENDMENT NO. 4) ACM Government Opportunity Fund, Inc. -------------------------------------------------------------------------------- (Name of Issuer) Common Stock -------------------------------------------------------------------------------- (Title of Class of Securities) 000918 102 -------------------------------------------------------------------------------- (CUSIP Number) Michael A. Conway Aon Advisors, Inc. 200 East Randolph Drive Chicago, Illinois 60601 (312) 381-3000 -------------------------------------------------------------------------------- (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) July 18, 2003 -------------------------------------------------------------------------------- (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 which is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(b)(3) or (4), check the following box / /. Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7(b) for other parties to whom copies are to be sent. (Continued on following pages) CUSIP NO. 000918 102 SCHEDULE 13D -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) AON CORPORATION 36-3051915 -------------------------------------------------------------------------------- 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) Not Applicable -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 4,155,636 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 4,155,636 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,155,636 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 32.5% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) HC, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 SCHEDULE 13D -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) AON ADVISORS, INC. 54-1392321 -------------------------------------------------------------------------------- 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) Not Applicable -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Virginia -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 4,155,636 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 4,155,636 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,155,636 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 32.5% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) IA, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 SCHEDULE 13D -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) COMBINED INSURANCE COMPANY OF AMERICA 36-2136262 -------------------------------------------------------------------------------- 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 BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Illinois -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 4,155,636 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 4,155,636 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,155,636 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 32.5% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) IC, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 SCHEDULE 13D -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) COMBINED SPECIALTY INSURANCE COMPANY -------------------------------------------------------------------------------- 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) Not Applicable -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Illinois -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 0 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 0 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 0 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 0.0% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) IC, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 This Amendment No. 4 (this "Amendment") amends and supplements the Schedule 13D filed with the Securities and Exchange Commission on December 10, 1999 (the "Schedule 13D") by Aon Corporation, a Delaware corporation ("Aon"), Aon Advisors, Inc., a Virginia corporation ("Advisors"), Combined Insurance Company of America, an Illinois corporation ("CICA"), and Combined Specialty Insurance Company, an Illinois corporation, formerly known as Virginia Surety Company ("CSIC", and together with Aon, Advisors and CICA, the "Filing Persons") as previously amended. The Schedule 13D as previously amended and this Amendment relate to the Common Stock (the "Common Stock") of ACM Government Opportunity Fund, Inc. (the "Issuer"). Capitalized terms used but not defined herein have the meanings ascribed to such terms in the Schedule 13D. Items 2, 4, 5, 6 and 7 of the Schedule 13D as previously amended are hereby amended and restated in their entirety as follows: ITEM 2. IDENTIFY AND BACKGROUND This Schedule is being filed on behalf of Aon Corporation, a Delaware corporation ("Aon"), Aon Advisors, Inc., a Virginia corporation ("Aon Advisors"), Combined Insurance Company of America, an Illinois corporation ("CICA"), and Combined Specialty Insurance Company, Inc., an Illinois corporation formerly known as Virginia Surety Company ("CSIC"). Aon Advisors, CICA and CSIC are wholly owned subsidiaries of Aon. Aon, Aon Advisors, CICA and CSIC are sometimes referred to herein as the "Filing Persons." Aon is a publicly held insurance holding company which, through subsidiaries, is a major provider of insurance, insurance brokerage, insurance underwriting, consulting and related services. Aon Advisors is a company incorporated under the laws of the State of Virginia which serves as an investment advisor to Aon, CICA, CSIC and their affiliates. CICA is a stock life insurance company incorporated under the laws of the State of Illinois and domiciled therein. CICA, together with its insurance subsidiaries, is a leading worldwide provider of supplemental accident and health insurance and life insurance products for individuals and also provides institutional investment and annuity products. CSIC is a stock life insurance company incorporated under the laws of the State of Illinois. CSIC, together with its insurance subsidiaries, is a leading worldwide provider of consumer extended warranty insurance and offers specialty insurance products. The Filing Persons share the same principal office and business address, 200 East Randolph Street, Chicago, Illinois 60601. Aon is a parent holding company in accordance with section 240.13d-1(b)(ii)(G) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). Aon Advisors is an investment adviser registered under section 203 of the Investment Advisers Act of 1940, as amended. CICA and CSIC are insurance companies as defined in section 3(a)(19) of the Exchange Act. During the past five years, none of the Filing Persons, and none of any of their executive officers or directors, have been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or have been party to a civil proceeding of a judicial or administrative body of competent jurisdiction resulting in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws. The names, addresses, offices and citizenship of the directors and officers of each of the Filing Persons (except for CSIC, which will cease to be a Filing Person upon the filing of this Amendment) are set forth on Annex I hereto. ITEM 4. PURPOSE OF TRANSACTION Subject to market conditions and limitations imposed by the securities laws, the Filing Persons have determined to implement a program to reduce their holdings of shares of Common Stock in open-market or other transactions over the longer term. Except as set forth above, none of the Filing Persons has any current plans or proposals which relate to or would result in any matter described in paragraphs (a) through (j) of Item 4 of Schedule 13D under the Exchange Act. The Filing Persons may, in the future, for any reason and in their sole discretion, change such intentions and/or formulate additional plans and proposals relating to one or more matters described in such paragraphs. ITEM 5. INTEREST IN SECURITIES OF THE ISSUER See rows 7 through 11 and row 13 on pages 2 through 5. The Issuer's Quarterly Report dated June 27, 2003 states that, as of April 30, 2003, there were 12,774,253 shares of Common Stock outstanding. The percentage ownership of Aon, Aon Advisors, CICA and CSIC was derived using this number of shares of Common Stock outstanding. Pursuant to an Investment Advisory Agreement between Aon Advisors and CICA, Aon Advisors is invested in, on behalf of and as investment adviser to CICA, 4,155,636 shares of Common Stock. Pursuant to an Investment Advisory Agreement between Aon Advisors and CSIC, Aon Advisors has in the past invested in, on behalf of and as investment advisor to CSIC, certain additional shares of Common Stock. CSIC, however, no longer owns any shares of Common Stock, and thus, by the filing of this Amendment, will cease to be a Filing Person. Because Aon is the parent holding company to CICA, Aon indirectly beneficially owns all shares of Common Stock held by CICA. By reason of the purchases of Common Stock made on behalf of CICA, as of the date of this Amendment, Aon, Aon Advisors and CICA share the power to vote or direct the vote and the power to dispose or direct the disposition of 4,155,636 shares of Common Stock, or 32.5% of the total outstanding shares of Common Stock as of April 30, 2003. During the sixty day period preceding the date of this Amendment, none of the Filing Persons effected any transactions in any shares of Common Stock other than the following sales by Aon Advisors on behalf of CICA: Date Number of Shares Price Per Share ($) ---- ---------------- ------------------- 07/18/03 19,800.00 8.6932 07/17/03 13,600.00 8.6762 07/16/03 25,700.00 8.7474 07/15/03 12,600.00 8.8690 07/14/03 6,600.00 8.9758 07/11/03 10,900.00 8.9984 07/10/03 10,500.00 8.9938 07/09/03 2,000.00 9.0925 07/08/03 17,200.00 9.1022 07/07/03 6,100.00 9.2787 ---------- 125,000.00 ========== ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO SECURITIES OF THE ISSUER Aon Advisors and CICA are parties to an Investment Advisory Agreement dated May 1, 1992 pursuant to which Aon Advisors serves as investment adviser to CICA. A copy of this agreement is filed as Exhibit A to this Schedule. ITEM 7. MATERIAL TO BE FILED AS EXHIBITS A. Investment Advisory Agreement dated May 1, 1992 between Aon Advisors and CICA (incorporated by reference to the Schedule 13D filed by the Filing Persons on December 10, 1999) B. [Intentionally Omitted] C. Joint Filing Agreement dated December 10, 1999 among each of the Filing Persons (incorporated by reference to the Schedule 13D filed by the Filing Persons on December 10, 1999) SIGNATURE After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct. AON CORPORATION Date: July 22, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway Senior Vice President and Senior Investment Officer AON ADVISORS, INC. Date: July 22, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway President COMBINED INSURANCE COMPANY OF AMERICA Date: July 22, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway Senior Vice President COMBINED SPECIALTY INSURANCE COMPANY Date: July 22, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway Senior Vice President ANNEX I OFFICERS AND DIRECTORS Set forth below is a list of each of the directors and officers of each of the Filing Persons (except for CSIC, which will cease to be a Filing Person upon the filing of the Amendment). Unless otherwise indicated, each person identified on this Annex I shares the business address of the Filing Persons and is a citizen of the United States. Name Title Citizenship ---- ----- ----------- Aon Corporation: Patrick G. Ryan Chairman and Chief Executive Officer and Director Michael D. O'Halleran President and Chief Operating Officer and Director David P. Bolger Executive Vice President and Chief Financial Officer June E. Drewry Executive Vice President and Chief Information Officer Raymond I. Skilling Executive Vice President and Chief Counsel Michael A. Conway Senior Vice President and Senior Investment Officer Jeremy G.O. Farmer Senior Vice President and Head of Human Resources Joseph J. Prochaska, Jr. Senior Vice President and Controller Carl J. Bleecher Vice President - Internal Audit Kevann M. Cooke Vice President and Corporate Secretary Vaughn Hooks Vice President - Taxes Sean P. O'Neill Vice President - Financial Relations John A. Reschke Vice President - Compensation and Benefits Diane M. Aigotti Treasurer Richard L. Vodziak Assistant Vice President - Taxes Richard E. Barry Assistant Secretary Edgar D. Jannotta Director P.J. Kalff Director Lester B. Knight Director J. Michael Losh Director R. Eden Martin Director Andrew J. McKenna Director Robert S. Morrison Director Richard C. Notebaert Director John W. Rogers, Jr. Director George A. Schafer Director Carolyn Y. Woo Director Aon Advisors: Michael A. Conway President and Director Daniel T. Busiel Senior Vice President/Fixed Income and Director David C. Greenberg Senior Vice President and Director Brian H. Lawrence Treasurer Leonor de la Torre Secretary CICA: Richard M. Ravin Chairman, President and Chief Executive Officer and Director David P. Bolger Executive Vice President and Chief Financial Officer Steven E. Lippai Executive Vice President and Director Raymond I. Skilling Executive Vice President, Chief Counsel and Director Ronald G. Agypt Senior Vice President and Managing Director - 7th Essential USA Michael A. Conway Senior Vice President, Senior Investment Officer and Director Alastair M. Cumming Senior Vice President - National Sales Manager - Life and Health USA, and Director Clive G. Robinson Managing Director, Senior Vice President Europe and Pacific, and Director Diane M. Aigotti Treasurer John J. Hogan Vice President and Controller Ronald D. Markovits Vice President - Government Relations and Law, and Corporate Secretary Patrick G. Ryan Director David L. Cole Director Harvey N. Medvin Director