You might have more control over the situation than you think.

The most difficult - and yet crucial - part of any change management initiative is making effective changes in the attitudes and behaviors of the people involved.  After all, they've been working away at their jobs, sometimes for years, and it can intimidating - and a little scary - to learn that they may have to change everything they know in order to thrive in the 'new world'.

If that wasn't hard enough, what can make change even more difficult is existing conflict between individuals.  I'm talking about the often long-standing conflict that tends to be based in fundamental personality clashes, working styles and work history, typically between heads of competing departments or teams.  In a normal working environment, this kind of conflict can be contained, but in a changing environment, which can involve new teams, new responsibilities, and different reporting structures, it can be a real roadblock to moving forward efficiently and effectively.

So what can you do, as a change management professional?

My approach, as soon as I identify one of these conflicts (and if you've done your information-gathering correctly, they become evident pretty early on in the process), is to encourage the two parties to resolve their conflict, for the sake of themselves and their teams.  I work with both parties and start by asking them to ask themselves the following questions:

1.  Why is this conflict happening?  90% of the time, these kinds of conflicts are based in perceived insecurity or anxiety based on their work history together.  One or both parties feels they have to protect themselves from a percevied threat, and that if they abandon the conflict or make an effort to drop their guard, 'bad things' will happen.  If you can get to the bottom of the perceived threat, the involved parties can begin to addres and resolve it.

2.  What is my [the participant's] role in the conflict?  It's easy to blame the other person for a conflict, but most people, when asked to think about it, will eventually admit that they haven't been entirely blameless.  Encouraging each individual to take responsibility for how they've contributed to the conflict is the first step to changing their behavior.

3.  What outcome am I (the participant) looking for?  Ask each participant, separately, what 'the best outcome' of the situation would look like. Their knee-jerk, emotional reaction may be "For so-and-so to get fired!" but when asked to think about it, most people will eventually admit that they want something fairly simple, like "I'd like not to feel undermined with my boss", or "Our public and private opinions remain aligned".

4.  What does the other person want?  Ask each participant to put themselves in the other person's shoes.  This serves to remind each participant that there are two sides to every conflict.  It helps lay the groundwork for empathy which will be critical for the next stage - a face-to-face conversation.

5.  Is there any reason a frank, private discussion won't help?  Sometimes, the two parties have never had a friendly conversation about anything.  Putting the two together in a room, alone - and without everyone else in the office knowing that they're having a conversation - and encouraging them to discuss why they're having trouble working together and what things they may have in common can be a surprisingly effective first step to achieving at least a tacit working truce.  

You might also consider having a third party there to facilitate the conversation.  That might be you or a trusted HR partner.  An important part of the conversation will be for both individuals to imagine what working well together without conflict might look like.  One way to encourage this is to have each person complete the sentence:  "When X and I are working well together..." in a brainstorming fashion, then share their answers with one another.  The last part will be a commitment to change one behavior:  "I commit to checking with X before speaking on his behalf or committing him to work" or "I commit to keeping the agreements we've made during a team meeting".  Both parties also need to decide how they will continue their communication - regular one-on-ones can provide a good forum for that.

Now, I'm no Pollyanna, and I know that not every workplace conflict is solvable - sometimes one or both people are simply unhappy or a poor fit and the change process is a good time for them to move on.  However, if you're working with good individual contributors or top performers, making an effort to resolve the conflict first can save a good deal of time and money later.