The White House on Thursday announced ambitious plans to create the U.S. Space Force as a sixth, separate military warfighting service by 2020. Military leaders and experts have questioned the wisdom of launching an expensive, bureaucratic new service branch. Vice President Mike Pence announced the new force during a Pentagon speech, fleshing out an idea that President Donald Trump has extolled in recent months as he vowed to ensure American dominance in space. Pence described space as a domain that was once peaceful and uncontested but has now become crowded and adversarial. The last time the U.S. created a new uniformed military service was in 1947. Defense Secretary Jim Mattis has endorsed steps to reorganize the military's space-warfighting forces and create a new command, but he previously opposed launching an expensive new service. The military's role in space has been under scrutiny because the United States is increasingly reliant on orbiting satellites that are difficult to protect. U.S. intelligence agencies reported earlier this year that Russia and China were pursuing nondestructive and destructive" anti-satellite weapons for use during a future war. And there are growing worries about cyberattacks that could target satellite technology. Much of the military's current space power is wielded by the Air Force Space Command, which ... has about 38,000 personnel and operates 185 military satellite systems, including the Global Positioning System and communications and weather satellites.