From Halopedia, the Halo wiki
Star-hopping was a strategy formulated by the Didact during the course of the Human-Forerunner War. Using strategically placed shield worlds, the fleets of the Warrior-Servants would be able to wage campaigns of destruction against strategically vital worlds to the human empire, and ignore everything else. The plan eventually reduced the humans to their capital of Charum Hakkor. When the Forerunners learned about the Flood, the Didact proposed star-hopping to the Ecumene Council as a means to counter the parasite, but the Master Builder Faber, leading the radical Builder faction, proposed the creation of a super-weapon that would eventually become the Halo Array.
The Didact's "star-hopping" plan is very similar to the "island-hopping plan" that American naval forces in the Pacific in World War II made, right down to its name. American forces would attack important Japanese-held islands and ignore less important ones, using the conquered islands to stage bombing runs on the next island and forcing those to capitulate.
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