Thanks for the question.

It's important to understand the context in which Mitchell said his comment, and a bit about Mitchell himself.

Mitchell was born in 1879 and was old enough to enlist in the U.S. Army during the Spanish-American War. Unlike many of his contemporaries, he stayed in the military after that war's end. Mitchell, after initially enlisting with a Wisconsin regiment, joined the U.S. Army Signal Corps and with his father's influence, got a commission.

After the war, Mitchell was posted to Alaska, where the military was constructing WAMCATS, the Washington-Alaska Military Communications And Telegraph System. The gold rushes of the late 19th and early 20th centuries had brought thousands of people into Alaska and the Yukon, but the only telegraphic communications to that region were through Canada. The United States didn't like the idea of relying on Canadian links, which could be severed in the event of war with Great Britain, and so it wanted to construct its own system.

Mitchell worked on this system, snowshoeing between telegraph stations, mushing along frozen rivers, and generally becoming acquainted with the territory.

Just 35 years before, U.S. Secretary of State William Henry Seward had believed that in order to fulfill its manifest destiny to control all of North America, the United States needed advance positions to defend its territory and project power beyond North America. Seward believed that acquisition of Alaska, Hawaii, Greenland and the Danish Virgin Islands would accomplish this goal.

Seward was able to negotiate a treaty of cession with Russia, which was an interested seller, but Congressional fights with the Johnson administration and an ill-timed Caribbean hurricane meant Seward could only negotiate the purchase of Alaska. The other locations would await the future.

After leaving Alaska in 1904, Mitchell was sent to the Army Signal School in Fort Leavenworth, Kansas, where he became an instructor. He was an early adopter of the idea that aviation would transform warfare (this idea was not unique to him), and taught his students as much. Mitchell was present at the Wrights' military demonstration flight in 1908, and in 1912 he was chosen for the U.S. Army's general staff. At the time, aviation was a part of the Signal Corps, because it was believed that observation was its primary duty.

Mitchell stayed involved with aviation and during World War I continued to rise through the ranks as a commander. He commanded all American air units in France and enjoyed good relations with the Europeans (though less so with his commanders, to whom he was abrasive).

After the war, he remained a proponent of air power and in 1919 urged his commanding officer to organize a flight from New York to Nome, Alaska, the first such organized flight in American history. Despite mechanical, weather and logistical problems, the flight took place in 1920 and was a success. Four years later, Mitchell organized an around-the-world flight that used Alaska as a significant portion of its route.

As this was happening, the idea of air power was gaining prominence worldwide. A year after the Nome flight, Italian Giulio Douhet published The Command of the Air, an air-power theory book that became enormously influential. Douhet argued that defense against the bomber was impossible because the sky was so large that adequate defenses could never be mustered against a large fleet of aircraft. Furthermore, he theorized that terror bombing, targeted at civilians instead of military targets, would lead nations to surrender quickly. If "the bomber always gets through" (as Douhet's theory was later summarized), the nations that mustered the largest fleets of heavy bombers at the outbreak of war would win. If defense was impossible, the only defense was a good offense.

Mitchell met Douhet in 1922, and Command of the Air was influential on him as it was on thinkers all around the world. Brett Holman's The Next War in the Air: Britain's Fear of the Bomber, 1908-1941 is a good one for the British perspective; Michael Sherry's award-winning The Rise of American Air Power: The Creation of Armageddon is good for the American perspective.

Six years after meeting Douhet, Mitchell wrote his influential paper "America, Air Power and the Pacific." While never published in wide circulation, Mitchell outlines what would become America's approach to Alaska air power for the following 65 years.

As Mitchell points out, "Outside of the United States proper, Alaska is our most important point with regard to our protection against Asia. The distance to Hawaii from Alaska is only 1,300 miles, as compared to 2,000 miles from our Pacific coast. Alaska is within striking distance of any place we want to approach in Asia, either commercially or in a military way."

That's the key point of your first question. By the late 1920s, it was clear that Alaska's geography, roughly equidistant from the major cities of east Asia, Europe and North America, made it critical for air travel. While Alaska was prized in the 1920s for its ability to hold fueling stations, Mitchell points out that the pace of technology will change things further. "The vast leagues of the Pacific are shrinking continually under the magic of scientific aircraft development. The day is not far off when neither months, weeks nor days will be used in computing the trip (between the United States and Asia), but hours alone."

Even if fueling is not necessary in Alaska, the shortest route still flies over that territory, Mitchell realized. He began promoting the idea that Alaska needed to have military air bases in order to serve effectively in the next war. At the same time, Alaska's nonvoting Delegate to Congress, Anthony Dimond, introduced a bill to build airfields in Alaska to serve the military and commerce, but it didn't go anywhere. In 1934, Col. Henry Arnold led a flight of 10 B-10 bombers from Washington, D.C. to Fairbanks, Alaska, to help build the case for these airfields. This was the first time a flight to Alaska did not need to stop in Canada.

Following the success of this flight, Rep. James Mark Wilcox, D-Florida, introduced a bill calling for airfield construction in Alaska (among other places). He introduced it soon after the start of the 74th Congress, and it was referred to committee. On Feb. 11, 1935, this was where Mitchell declared in support of the bill, "Alaska is the most central place in the world for aircraft, and that is true of Europe, Asia or North America. I believe, in the future, he who holds Alaska will hold the world, and I think it is the most strategic place in the world."

Wilcox's bill became law in August 1935, and construction of bases in Fairbanks, Anchorage and Kodiak followed. They were followed by others as war broke out in Europe, and by the time the United States entered the war, they were ready for operation. It's difficult to say whether Mitchell's testimony was critical to the passage of the bill, but it's easy to say that the bill itself was critical to American defense of Alaska. Without it, bases might not have been ready for use when war began.

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He said that because of the tremendous mineral resources of Alaska (gold and oil being discovered in the 1890s and 1902, respectively) plus the threat that a hostile Alaska could pose to Canada/the US because of its geographic position. Mitchell also thought that from Alaska a nation could control the Pacific and easily project power over to the the Asian mainland. From an aviation standpoint Alaskan-based aircraft could, in his view, deter and attack hostile ships crossing the Pacific and utterly dominate the region.

Mitchell isn't correct, though. His statement on Alaska is identical to the many other overstatements and hyperboles visible in every topic he ever wrote or spoke about. His autobiography is particularly embellished, as is Winged Defense, his seminal work. You have to filter out Mitchell's own bias and self-interests whenever you read his material because the man is obviously a self-promoter willing to lie if it serves his interests.