Having trouble using coroutines, making unity hang

Hello and thank you for reading this. I have some trouble running a coroutine in my rpg game. I'm still making the prototype(trying to make everything function on a basic level). What i've done so far,is make the player controlled units attack a target that you select by pressing a button, and then waiting for the user to actually target the unit to attack. I have limited experience using coroutines, so any input or explanation would be useful.The code for the targeting system is below:

 void Update () {
         
     if(Input.GetButtonDown("Fire1"))
         {    
             TargetRay=Camera.main.ScreenPointToRay(Input.mousePosition);
             if(Physics.Raycast (TargetRay,out hit,100,enemymask)){
                   Target(hit.collider.gameObject);
                  Friendly=false;
                  // Debug.Log ("Enemy!");
             }
             else if(Physics.Raycast (TargetRay,out hit,100,playermask)){
                  Target(hit.collider.gameObject);
                  Friendly=true;
                  // Debug.Log("Player!");
                  
             }
     
         }
     
     }
     public GameObject Target(GameObject target){
         if(selectedTarget==null){
         selectedTarget=target;
         }
         else{
             Deselect();
             selectedTarget=target;
         }
             
         selectedTarget.renderer.material.color=Color.red;
         
         return selectedTarget;
     }
     
     public void Deselect(){
         selectedTarget.renderer.material.color=Color.gray;
             selectedTarget=null;
     }
         
     
 }

The code for the combat system is below:

 void Update () {
         if(Input.GetButtonDown("Attack")){
             //Targeting.selectedTarget.renderer.material.color=Color.gray;
             //Targeting.selectedTarget=null;
             origin=TurnSystem.GetCurrentOrigin();
             OriginStats=origin.GetComponent("Stats")as Stats;
             Debug.Log ("Select a target to attack for "+OriginStats.Damage+"damage" );
             
             StartCoroutine(Attack (origin));
         }
             
         }
         
         
         
         
     public IEnumerator Attack(GameObject Go){
             //Debug.Log ("Select a target to Attack");
             if(Targeting.selectedTarget!=null){
                 Targeting.Deselect();
             }
             yield return StartCoroutine(WaitForTarget());
             target=Targeting.selectedTarget;
             TargetStats=target.GetComponent("Stats")as Stats;
             TargetStats.HP=TargetStats.HP-OriginStats.Damage;
             //Go.transform.position=target.transform.position;   //should wait for attack animation to finish
            // Go.transform.position=OriginalPosition;
             OnAttackEnd();
     }
     
     public IEnumerator WaitForTarget(){
         
         while(Targeting.selectedTarget==null){
             if(Targeting.selectedTarget!=null && Targeting.Friendly==true){
                     Debug.Log("The target you selected is friendly.Please select an enemy target.");
                     Targeting.Deselect();
             }
             
             else if (Targeting.selectedTarget!=null && Targeting.Friendly==false){
                     Debug.Log ("Target is",Targeting.selectedTarget);
                     yield break;
                 }
                 
                 
             }
             yield return 0 ;
         }

Thanks!