EMPLOYMENT AGREEMENT between J. MARK LESTER and CHESAPEAKE ENERGY CORPORATION Effective July 1, 2003 EMPLOYMENT AGREEMENT

Exhibit 10.2.10

EMPLOYMENT AGREEMENT

between

J. MARK LESTER

and

CHESAPEAKE ENERGY CORPORATION

Effective July 1, 2003

EMPLOYMENT AGREEMENT

THIS AGREEMENT is made effective July 1, 2003, between CHESAPEAKE ENERGY CORPORATION, an Oklahoma corporation (the “Company”), and J. MARK LESTER an individual (the “Executive”).

W I T N E S S E T H:

WHEREAS, the Company desires to retain the services of the Executive and the Executive desires to make the Executive’s services available to the Company.

NOW, THEREFORE, in consideration of the mutual promises herein contained, the Company and the Executive agree as follows:

1. Employment. The Company hereby employs the Executive and the Executive hereby accepts such employment subject to the terms and conditions contained in this Agreement. The Executive is engaged as an employee of the Company, and the Executive and the Company do not intend to create a joint venture, partnership or other relationship which might impose a fiduciary obligation on the Executive or the Company in the performance of this Agreement.

2. Executive’s Duties. The Executive is employed on a full-time basis. Throughout the term of this Agreement, the Executive will use the Executive’s best efforts and due diligence to assist the Company in achieving the most profitable operation of the Company and the Company’s affiliated entities consistent with developing and maintaining a quality business operation.

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3. Other Activities. Except as provided in this Agreement or approved by the Board, the Executive agrees not to: (a) engage in other business activities independent of the Company which individually or in the aggregate require a substantial portion of the Executive’s time; (b) except for passive investments which do not violate this Agreement, serve as a general partner, officer, employee, director or member of any corporation, partnership, company or firm; or (c) directly or indirectly invest, participate or engage in the Oil and Gas Business. For purposes of this Agreement the term “Oil and Gas Business” means: (i) producing oil and gas; (ii) drilling, owning or operating an interest in oil and gas leases or wells; (iii) providing material or services to the Oil and Gas Business; (iv) refining, processing or marketing oil or gas; or (v) owning an interest in or assisting any corporation, partnership, company, entity or person in any of the foregoing. The foregoing will not prohibit: (w) ownership of publicly traded securities; (x) ownership of royalty interests where the Executive owns the surface of the land covered by the royalty interest and the ownership of the royalty interest is incidental to the ownership of such surface estate; (y) ownership of royalty interests, overriding royalty interests, working interests or other interests in oil and gas owned prior to the Executive’s date of first employment with the company and disclosed to the Company in writing; or (z) ownership of royalty interests, overriding royalty interests, working interests or other interests in oil and gas acquired by the Executive through a bona fide gift or inheritance.

4. Executive’s Compensation. The Company agrees to compensate the Executive as follows:

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(a) the acquisition by any individual, entity or group (within the meaning of Section 13(d)(3) or 14(d)(2) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) (a “Person”) of beneficial ownership (within the meaning of Rule 13d-3 promulgated under the Exchange Act) of twenty percent (20%) or more of either (i) the then outstanding shares of common stock of the Company (the “Outstanding Company Common Stock”) or (ii) the combined voting power of the then outstanding voting securities of the Company entitled to vote generally in the election of directors (the “Outstanding Company Voting Securities”). For purposes of this paragraph, the following acquisitions by a Person will not constitute a Change of Control: (i) any acquisition directly from the Company; (ii) any acquisition by the Company; (iii) any acquisition by or sponsored by Mssrs. Aubrey K. McClendon and/or Tom L. Ward; (iv) any acquisition by any employee benefit plan (or related trust) sponsored or maintained by the Company or any corporation controlled by the Company; or (v) any acquisition by any corporation pursuant to a transaction which complies with clauses (i), (ii) and (iii) of paragraph (c) below;

(b) the individuals who, as of June 15, 2003, constitute the board of directors (the “Incumbent Board”) cease for any reason to constitute at least a majority of the board of directors. Any individual becoming a director subsequent to the date hereof whose election, or nomination for election by the Company’s shareholders, is approved by a vote of at least a majority of the directors then comprising the Incumbent Board will be considered a member of the Incumbent Board as of the date hereof, but any such individual whose initial assumption of office occurs as a result of an actual or threatened election contest with respect to the election or removal of directors or other actual or threatened solicitation of proxies or consents by or on behalf of a Person other than the Incumbent Board will not be deemed a member of the Incumbent Board as of the date hereof;

(c) the consummation of a reorganization, merger, consolidation or sale or other disposition of all or substantially all of the assets of the Company (a “Business Combination”), unless following such Business Combination: (i) all or substantially all of the individuals and entities who were the beneficial owners, respectively, of the Outstanding Company Common Stock and Outstanding Company Voting Securities immediately prior to such Business Combination beneficially own, directly or indirectly, more than sixty percent (60%) of, respectively, the then outstanding shares of common stock and the combined voting power of the then outstanding voting securities entitled to vote generally in the election of directors, as the case may be, of the corporation resulting from such Business Combination (including, without limitation, a corporation which as a result of such transaction owns the Company

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or all or substantially all of the Company’s assets either directly or through one or more subsidiaries) in substantially the same proportions as their ownership, immediately prior to such Business Combination of the Outstanding Company Common Stock and Outstanding Company Voting Securities, as the case may be, (ii) no Person (excluding any corporation resulting from such Business Combination or any employee benefit plan (or related trust) of the Company or such corporation resulting from such Business Combination) beneficially owns, directly or indirectly, twenty percent (20%) or more of, respectively, the then outstanding shares of common stock of the corporation resulting from such Business Combination or the combined voting power of the then outstanding voting securities of such corporation except to the extent that such ownership existed prior to the Business Combination and (iii) at least a majority of the members of the board of directors of the corporation resulting from such Business Combination were members of the Incumbent Board at the time of the execution of the initial agreement, or of the action of the Board, providing for such Business Combination; or,

(d) the approval by the shareholders of the Company of a complete liquidation or dissolution of the Company.

5. Term. The employment relationship evidenced by this Agreement is an “at will” employment relationship and the Company reserves the right to terminate the Executive at any time with or without cause as provided herein. In the absence of such termination, this Agreement will extend for a term of three (3) years and three (3) months commencing on July 1, 2003, and ending on September 30, 2006 (the “Expiration Date”).

6. Termination. This Agreement will continue in effect until the expiration of the term stated at paragraph 5 of this Agreement unless earlier terminated pursuant to this paragraph 6.

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7. Confidentiality. The Executive recognizes that the nature of the Executive’s services are such that the Executive will have access to information which constitutes trade secrets, is of a confidential nature, is of great value to the Company or is the foundation on which the business of the Company is predicated. The Executive agrees not to disclose to any person other than the Company’s employees or the Company’s

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legal counsel nor use for any purpose, other than the performance of this Agreement, any confidential information (“Confidential Information”). Confidential Information includes data or material (regardless of form) which is: (a) a trade secret; (b) provided, disclosed or delivered to Executive by the Company, any officer, director, employee, agent, attorney, accountant, consultant, or other person or entity employed by the Company in any capacity, any customer, borrower or business associate of the Company or any public authority having jurisdiction over the Company of any business activity conducted by the Company; or (c) produced, developed, obtained or prepared by or on behalf of Executive or the Company (whether or not such information was developed in the performance of this Agreement) with respect to the Company or any assets oil and gas prospects, business activities, officers, directors, employees, borrowers or customers of the foregoing. However, Confidential Information shall not include any information, data or material which at the time of disclosure or use was generally available to the public other than by a breach of this Agreement, was available to the party to whom disclosed on a non-confidential basis by disclosure or access provided by the Company or a third party, or was otherwise developed or obtained independently by the person to whom disclosed without a breach of this Agreement. On request by the Company, the Company will be entitled to the return of any Confidential Information in the possession of the Executive. The Executive also agrees that the provisions of this paragraph 7 will survive the termination, expiration or cancellation of this Agreement for a period of three (3) years. The Executive will deliver to the Company all originals and copies of the documents or materials containing Confidential Information. For purposes of paragraphs 7, 8, and 9 of this Agreement, the Company expressly includes any of the Company’s affiliated corporations, partnerships or entities.

8. Noncompetition. For a period of six (6) months after the Executive is no longer employed by the Company as a result of either the termination of or resignation by the Executive, the Executive will not acquire, attempt to acquire or aid another in the acquisition or attempted acquisition of an interest in oil and gas assets, oil and gas production, oil and gas leases, mineral interests, oil and gas wells or other such oil and gas exploration, development or production activities within any spacing unit in which the Company owns an oil and gas interest on the date of the resignation or termination of the Executive. In addition, the Executive will not solicit, induce, entice or attempt to entice any employee, contractor, customer, vendor or subcontractor to terminate or breach any relationship with the Company or the Company’s affiliates for the Executive’s own account or for the benefit of another party. The Executive further agrees that the Executive will not circumvent or attempt to circumvent the foregoing agreements by any future arrangement or through the actions of a third party. The foregoing will not prohibit the activities which are expressly permitted by the last sentence of paragraph 3 of this Agreement.

9. Proprietary Matters. The Executive expressly understands and agrees that any and all improvements, inventions, discoveries, processes, know-how or intellectual property that are generated or conceived by the Executive during the term of this Agreement, whether generated or conceived during the Executive’s regular working hours or otherwise, will be the sole and exclusive property of the Company. Whenever

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requested by the Company (either during the term of this Agreement or thereafter), the Executive will assign or execute any and all applications, assignments and or other instruments and do all things which the Company deems necessary or appropriate in order to permit the Company to: (a) assign and convey or otherwise make available to the Company the sole and exclusive right, title, and interest in and to said improvements, inventions, discoveries, processes, know-how, applications, patents, copyrights, trade names or trademarks; or (b) apply for, obtain, maintain, enforce and defend patents, copyrights, trade names, or trademarks of the United States or of foreign countries for said improvements, inventions, discoveries, processes or know-how. However, the improvements, inventions, discoveries, processes or know-how generated or conceived by the Executive and referred to above (except as they may be included in the patents, copyrights or registered trade names or trademarks of the Company, or corporations, partnerships or other entities which may be affiliated with the Company) shall not be exclusive property of the Company at any time after having been disclosed or revealed or have otherwise become available to the public or to a third party on a non-confidential basis other than by a breach of this Agreement, or after they have been independently developed or discussed without a breach of this Agreement by a third party who has no obligation to the Company or its affiliates. The foregoing will not prohibit any activities which are expressly permitted by the last sentence of paragraph 3 of this Agreement during the term of this Agreement.

10. Arbitration. The parties will attempt to promptly resolve any dispute or controversy arising out of or relating to this Agreement or termination of the Executive by the Company. Any negotiations pursuant to this paragraph 10 are confidential and will be treated as compromise and settlement negotiations for all purposes. If the parties are unable to reach a settlement amicably, the dispute will be submitted to binding arbitration before a single arbitrator in accordance with the Employment Dispute Resolution Rules of the American Arbitration Association. The arbitrator will be instructed and empowered to take reasonable steps to expedite the arbitration and the arbitrator’s judgment will be final and binding upon the parties subject solely to challenge on the grounds of fraud or gross misconduct. Except for damages arising out of a breach of paragraphs 7, 8 or 9 of this Agreement, the arbitrator is not empowered to award total damages (including compensatory damages) which exceed two hundred percent (200%) of compensatory damages and each party hereby irrevocably waives any damages in excess of that amount. The arbitration will be held in Oklahoma County, Oklahoma. Judgment upon any verdict in arbitration may be entered in any court of competent jurisdiction and the parties hereby consent to the jurisdiction of, and proper venue in, the federal and state courts located in Oklahoma County, Oklahoma. Each party will bear its own costs in connection with the arbitration and the costs of the arbitrator will be borne by the party who the arbitrator determines did not prevail in the matter. Unless otherwise expressly set forth in this Agreement, the procedures specified in this paragraph 10 will be the sole and exclusive procedures for the resolution of disputes and controversies between the parties arising out of or relating to this Agreement. Notwithstanding the foregoing, a party may seek a preliminary injunction or other provisional judicial relief if in such party’s judgment such action is necessary to avoid irreparable damage or to preserve the status quo.

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11. Miscellaneous. The parties further agree as follows:

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IN WITNESS WHEREOF, the undersigned have executed this Agreement effective the date first above written.

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