The Jizyah also has a part to play in that but yes, as I said and you repeated, the jizyah also covers military expenses, the same military which protects the non-muslims. In Islam, a muslim, when living in a true islamic state, MUST answer the call for war, whether it is to defend their borders or to fight against an oppressive regime. A non-muslim is under no such obligation, also the jizya covers the costs of the police force as does other revenues of funds by the government, the same police force, which, you guessed it, must look after both muslim and non-muslim citizens.