When my district assigns new principals to schools, they do no allow the principal to choose his/her administrative team

When my district assigns new principals to schools, they do no allow the principal to choose his/her administrative team?

This practice of leaving existing assistant principals at the site of newly assigned principals, assigning assistant principals randomly, or assigning the next assistant principals based on who is next on an eligibility list, places the incoming principal at a great disadvantage, especially when the new principal is assigned to a dysfunctional or failing school. 

There was an existing assistant principal when I arrived. Therefore, when I arrived at the new school I had to deal with the usual resistance to change that a new principal faces, and the added challenge of an existing assistant principal that aligns himself with the faculty and staff.  The entire staff and faculty has aligned themselves against me, the new comer because I threaten the culture that they have created and live daily, and the one person who I should be able to depend on to help me with the transition from outsider to new leader plays a role in interfering, delaying or blocking my transition. 

How do I successfully transition into the principalship where we can all work to gether as a team to establish a cooperative and collaborative climate that fosters student achievement ?  I need your strategies for:

1. How to get the existing administor to align himslf with me instead of the faculty? 
2. How to respond to the hostility and testing behaviors from the faculty