The enemy of my enemy is my friend

Related:

• Reconciled friend is a double
  enemy. --...
• An open enemy is better than a false friend.
  Greek...
• Money leant to a friend must be recovered from an enemy.
  German...
• Tell nothing to thy friend that thy enemy may not know.
  Danish...
• Be smart as a cat:
  Make a friend of your enemy's enemy...
• At the narrow passage there is no brother and no friend
  Arab...
• There is no such thing as an insignificant enemy.
  French...
• The State: friend to all,
  enemy of each one...
• Wine is a turncoat; first a friend,
  and then an enemy. --...