Sometimes a project can be so large in scale that a Scrum approach may seem impractical.
And you are right in a sense, if you think this. Yet there is a workaround. For a project that will require a massive amount of work, you will need enough employees to handle the workload. But Scrum teams must be limited to 7 people, plus or minus 2. There is a solution.
Perhaps you’ve seen a Russian nesting doll before. It’s one large doll that houses increasingly smaller dolls inside of it. They’re the same shape, just smaller in size. And this is the exact principle that you should look to in order to circumvent the restrictions of Scrum. By adding on more teams to the main team, you can have multiple insulated Scrum management teams overseeing each other, all using agile development methods.
The trick with building a Scrum of Scrums, however, is to ensure that no one team balloons in number by itself. Over-enrolled Scrum teams are almost always doomed to fail. For more information on this subject, watch the video from OpenView Labs featuring Jeff Sutherland.