Ah, perhaps if you're the MBA bean counter type. In reality, you should grow the business, because now you have much better back-office capabilities to support a more distributed, more diverse workforce. Don't be afraid of having lots of people, be afraid of not managing (supporting) them well, causing inefficiency.
You cannot merge 2 huge companies without significant layoffs; there are way too many overlapping job-responsibilities and it's impractical to somehow make that work. Maybe some kind of rare exception is a job that depends on physical location. If I already own a fleet ice-cream trunks in USA and I buy a company in Paris, I'm probably not going to layoff the paris ice-cream truck drivers...
There is a whole lot of overlapping administravia, you don't need 2 full sized legal departments, finance groups, HR group, marketing groups, sales groups and so on. Some layoffs will happen.
