You are cordially invited to attend a special meeting (the “Special

Stockholder Voting AgreementIn connection with the Merger Agreement, Harleysville Mutual, the owner as of such date ofapproximately 53.5% of the issued and outstanding shares of common stock of the Company, enteredinto a Stockholder Voting Agreement with Nationwide Mutual (the ‘‘Voting Agreement’’). Pursuant tothe Voting Agreement, Harleysville Mutual agreed to vote its shares of common stock of the Companyin favor of the proposal to adopt the Merger Agreement and in any other circumstances upon which avote, consent or other approval is sought with respect to the Merger Agreement, the Merger or othertransactions contemplated by the Merger Agreement. Solely for purposes of the Voting Agreement,Harleysville Mutual has agreed to designate Nationwide Mutual as Harleysville Mutual’s proxy andattorney-in-fact. Accordingly, unless the Voting Agreement is terminated as a result of the terminationof the Merger Agreement, Harleysville Mutual will vote its shares of common stock of the Company infavor of the proposal to adopt the Merger Agreement and the vote of no stockholder other thanHarleysville Mutual is required to adopt the Merger Agreement, and the Merger Agreement will beadopted at the Special Meeting. In addition, Harleysville Mutual has agreed to vote against (i) anymerger (other than the Mergers with Nationwide Mutual) or other sale of substantial assets, (ii) anyAlternative Transaction or Alternative Transaction Proposal, and (iii) any other action, agreement ortransaction that would reasonably be expected to result in a breach of any covenant, representation orwarranty or any other obligation or agreement of Harleysville Mutual contained in the MergerAgreement. The Voting Agreement will terminate upon the earlier of (i) the effective time of theMergers, and (ii) the termination of the Merger Agreement in accordance with its terms. Prior toentering into the Voting Agreement, the Company’s board of directors also approved the VotingAgreement, thereby making Section 203 (Business Combinations with Interested Stockholders) of theDelaware General Corporation Law inapplicable to the Merger.THE MERGERIntroductionWe are seeking adoption by our stockholders of the Merger Agreement by and among us,Nationwide Mutual, Harleysville Mutual, and Merger Sub. In connection with the Merger, ourstockholders will receive $60.00 in cash, without interest and less any applicable withholding taxes, foreach share of our common stock (other than (1) shares owned by the Company and its subsidiaries,(2) shares owned by Harleysville Mutual and its subsidiaries, which will be owned by NationwideMutual (as the surviving corporation of the Parent Merger), and (3) shares for which appraisal rightshave been properly exercised under Delaware law) outstanding immediately prior to the effective timeof the Merger.The Parties to the Merger AgreementHarleysville GroupHarleysville Group Inc.355 Maple AvenueHarleysville, Pennsylvania 19438Telephone: (215) 256-5000We are an insurance holding company headquartered in Pennsylvania which, together with oursubsidiaries, engages in the property and casualty insurance business on a regional basis in the UnitedStates. We are a Delaware corporation formed by Harleysville Mutual in 1979 as a wholly ownedsubsidiary. In May 1986, we completed an initial public offering of our common stock, reducing thepercentage of outstanding shares owned by Harleysville Mutual to approximately 70%. In April 1992,Harleysville Mutual completed a secondary public offering of a portion of the Company’s commonstock then owned by it, further reducing the percentage of outstanding shares owned by Harleysville23