Bermuda grass is an annual, fine textured "creeping grass" that grows and spreads rapidly during warm summer months. Similar to bent grass, this type of seed is commonly used on golf courses and sports fields.
Due to its rapid and sometimes widespread growth during warm months, Bermuda can quickly take over cool-season grasses while dormant. Herbicides are usually not as effective as simply hand-picking these weeds before they grow out of control.
To help prevent this, you can apply a pre-emergence just prior to its growing season (usually spring time) to prevent the seeds from germinating. However, the other extreme is to apply fluazifopbutyl or glyphosate to kill all of the grass, then reseed over it. This is only suggested if you plan on replanting or renovating your lawn afterwards.