Why didn’t the U.S. annex the entire Spanish East Indies at the end of the Spanish-American War?

Question

The Spanish East Indies were a large territory comprising mainly the Philippines,¹ plus a large scattering of Micronesian islands in four main groups (the Marianas, the Carolines, the Marshalls,² and the Palaus). Following Spain’s utter defeat in the 1898 Spanish-American War, the United States annexed (at least temporarily) almost the entirety of the Spanish colonial empire, including parts of the Spanish East Indies (the Philippines,³ plus the island of Guam⁴ in the southern Marianas); however, apart from Guam, Spain’s Micronesian holdings were left untouched, becoming the country’s only surviving colonial possessions outside of Africa.⁵

Given that the rest of Spain’s possessions in the East and West Indies were annexed by the United States, either temporarily (Cuba) or (quasi-)permanently (Puerto Rico, the Philippines,⁶ Guam), and that the U.S. did make an inroad (albeit a small one) into Spanish Micronesia by annexing Guam, why didn’t the U.S. go the full hog and annex the rest of Spain’s Micronesian islands?

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¹: Over which, however, Spain had little to no effective control outside of Manila.

²: Which were disputed with Germany.

³: Conveniently ignoring the fact that the independent Filipino government, an ally of the U.S. during the war, controlled literally the entirety of the Philippines except for the city of Manila, and quickly sparking another war, with hostilities continuing into the early 1930s in parts of the islands.

⁴: Which is why Guam is a separate territory from the Northern Mariana Islands (and also the reason the latter territory has the “Northern” in its name, as Guam is also one of the Mariana Islands - the southernmost one).

⁵: Having become essentially ungovernable with the loss of the colonial machinery in the Philippines, they were sold to Germany the following year, captured by Japan at the beginning of World War I, and eventually seized by the U.S. during (the Marshalls, Marianas, and Palaus) / at the end of (the Carolines) World War II (along with Guam and the Philippines, which had been overrun by Japan by a few days and a few months, respectively, after the outbreak of hostilities between the two countries in December 1941); following the latter war, they were assigned to the United States as a United Nations trust territory, most of which became independent in stages in the 1980s and 1990s as the countries of the Marshall Islands, the Federated States of Micronesia, and Palau, although the Marianas voted to instead become a U.S. commonwealth.

⁶: Yes, I am aware that the Philippines were granted self-government in the 1930s and full independence following World War II; however, as the original object of the United States had been to permanently annex the Philippines, and it continued to do so for a quarter-century after they first landed troops there, I’m putting the Philippines into the “(quasi-)permanent” category.

Answer 1

Spain basically gave up exactly the territories they had lost direct control of in the war:

• Cuba (situation was hopeless after the battle of Santiago)
• Puerto Rico (Spanish sovereignity relinquished in the armistice)
• the Philippines (situation hopeless as the fleet hat been destroyed in the battle of Manila Bay while most of the land was controled by Filippino revolutionaries and Manila was handed over to US forces after a mock battle),
• Guam (capitulated when surprised by American warships before the Spanish garrison was aware that war had been declared).

The peace treaty specified that Cuba was to be given independence while the other territories would pass to US control.

That said, the Spanish were initially not willing to give up control of all the Philippines (nor Cuba for that matter). They were only convinced after difficult negotiations. They may have planed to reconquer whatever territories they would retain from the Filippino revolutionaries later, or they may have planned to sell it, as the US delegation anticipated. This is exactly what they did with the rest of the Spanish East Indies when they sold it to Germany in 1899 for 25 million pesetas. In fact, warships form several other countries (especially Germany) had been present in Philippine waters during the war, waiting like vultures if there would be any leftovers for them to seize and turn into colonies after the war (which they might have done in case the Philippines would have been left to the Filippino revolutionaries as an independent republic instead of being occupied by the US).

This leaves the question, why did the US want Guam and not the rest of the islands. Guam had been an administrative hub of the Spanish colony, an important port of call for voyages between the Spanish colonies in the Americas and the Philippines. At the start of the war, the Americans were apparently under the impression that it was a mighty fortress. So Captain Glass had orders to seize it with his flotilla on his way to the Philippines while not bothering with the other islands. When he got there, he found the defenses in a sorry state and the Spanish garrison utterly unprepared to defend anything (and unaware of the existence of the state of war between Spain and the US).

Later, Guam was seen as a strategic port and military base in case of a war with Japan and a logistic waypoint to East and South East Asia.