Patents are territorial in nature. This means that a United States patent can only be enforced against conduct occurring in the United States, a Japanese patent can only be enforced against conduct occurring in Japan, and so on. Therefore, it may make sense in some circumstances to obtain a patent in more than one jurisdiction. For instance, if you wish to sell your invention in the United States, Canada and Europe then it may make economic sense to obtain patents in each of those jurisdictions. Similarly, if your biggest competitor has manufacturing facilities in India or Mexico it may make sense to obtain patents in those nations. This would create a barrier that may prevent your competitor from manufacturing your product.