In the summer of 1898, during the Spanish–American War, he served aboard the battleship Oregon, witnessing the sinking of the Spanish cruiser Reina Mercedes and the Battle of Santiago Bay.

After a final training cruise aboard the battleship Indiana, he graduated from the Naval Academy in 1899 and commenced the required two years of precommissioning sea duty as a passed midshipman.

After the 1906 training cruise he remained aboard Newark when it sailed to participate in the imposition of American military rule in Cuba following the resignation of President Tomás Estrada Palma.

In November 1906, he was assigned as senior engineering officer aboard the new battleship Kansas prior to its commissioning at Philadelphia Navy Yard on April 18, 1907.

Kansas conducted shakedown training near Provincetown, Massachusetts later that year, before joining the Great White Fleet at Hampton Roads, Virginia in December.

Pocahontas, engaged in the important, exacting and hazardous duty of' transporting and escorting troops and supplies to European ports through waters infested with enemy submarines and mines.

In mid-October, during gunnery drills in the Norfolk area, a powder explosion in the forward turret killed or injured every member of the gun crew.

Two of Trenton's crew, Ensign Henry Clay Drexler and Boatswain's Mate First Class George Cholister, were posthumously awarded the Medal of Honor for their unsuccessful efforts to prevent additional powder charges from detonating.

Dissatisfied with the existing guide to naval planning, Kalbfus decided to replace it by writing a book-length treatment of the precepts of logical thinking that could be applied to every military situation.

But, within the range of my own observation, both ashore and afloat, I saw that the keeping of office hours and the performance of sundry routine tasks were more in order than an intensive study of the Navy's real business."

Many staff members were dissatisfied with the new text, including Captain Raymond A. Spruance, who objected to Kalbfus' rejection of existing doctrine and to his cumbersome writing style.

[13] After assimilating all of the comments, Kalbfus submitted the book for publication under the title Sound Military Decision,[14] before departing the college on December 15, 1936 to assume a fleet command.

His successor, Rear Admiral Charles P. Snyder, spent a year reviewing the manuscript, then rewrote several chapters for clarity and published this revised edition in May 1938.

"[13] On January 2, 1937, he was advanced to the temporary rank of vice admiral as Commander Battleships, Battle Force, United States Fleet (COMBATSHIPS).

[17] A year later, Fleet Problem XX tested the defense of the Panama Canal with an elaborate three-week simulated battle in the South Atlantic and Caribbean beginning in February 1939.

Anticipating the conclusion of his tenure with the Battle Force, Kalbfus lobbied President Franklin D. Roosevelt, with endorsements added by the Chief of Naval Operations William D. Leahy, for Kalbfus to receive second assignment to serve as President of the Naval War College during deliberations involving the assignments of several key commanders on board the Houston.

Coincident with these developments, retired Captain Dudley W. Knox influenced the collateral duty appointment of Kalbfus to hold the functions of Director of Naval History from 1939.

[27] At the request of Stark and King in the immediate aftermath of the sinking of the USS Reuben James, Kalbfus remained on duty upon his administrative transfer to retired status on 1 December 1941.

[28] Kalbfus organized the Naval War College to inform the operational plans, as implemented by the seagoing fleet headquarters staffs in the Asiatic, Pacific, and Atlantic.

Having previously visited the British cryptographic facilities on the grounds of Bletchley Park, Western Approaches, and the Operational Intelligence Centre in London, Lieutenant Robert Weeks served as King's communications and intelligence officer while assigned from the Atlantic Fleet staff to organize the tracking organization in the Communications Annex of the Naval War College during the summer of 1941.

[29] Under the collaborative arrangements between King and Kalbfus in efforts to synthesize Atlantic Fleet operations with intelligence, the Naval War College provided the venue ashore which enabled Weeks to establish a key communications link with the equivalent tracking activities on the Chief of Naval Operations and War Plans Division staffs within the Navy Department.

[30] With the establishment of Sea Frontier Headquarters in conjunction with joint Army-Navy reorganization efforts, Kalbfus carried the multiple functions of President of the Naval War College.

Wartime conditions following the surprise attacks at Pearl Harbor created the mandate for Kalbfus to remain on active service on retired status in his multifaceted assignment as President of the Naval War College.

He remained based in Newport upon his subsequent relief as President of the Naval War College, Vice Admiral William S. Pye on November 2, 1942.

In this capacity, he addressed the Congress of the Daughters of the American Revolution on April 20, 1943, where he declared that Japan and Germany must be restrained by force from future surprise attacks.

When I am retired from the Navy I shall spend the rest of my days trying to teach the American people that their faith in humanity and high ethical standards are not enough, unless backed up with force.

[38] Vice Admiral Charles Wellborn, Jr. recalled that when appointed, Kalbfus "was commonly regarded as a good solid Naval Officer--not brilliant, but sound.

Its report to the Navy Department largely exonerated Rear Admiral Husband E. Kimmel, commander in chief of the Pacific Fleet at the time of the attack.

Forrestal concluded that both Kimmel and Stark had "failed to demonstrate the superior judgment necessary for exercising command commensurate with their rank and their assigned duties.

In 1947, he was appointed by President Harry S. Truman to succeed Pennsylvania Senator David A. Reed as a member of the American Battle Monuments Commission.