Consider a couple that qualifies for INA 319(b) [8 USC 1430(b)], which reads
(b) Any person, (1) whose spouse is (A) a citizen of the United States, (B) in the employment of the Government of the United States, or of an American institution of research recognized as such by the Attorney General, or of an American firm or corporation engaged in whole or in part in the development of foreign trade and commerce of the United States, or a subsidiary thereof, or of a public international organization in which the United States participates by treaty or statute, or is authorized to perform the ministerial or priestly functions of a religious denomination having a bona fide organization within the United States, or is engaged solely as a missionary by a religious denomination or by an interdenominational mission organization having a bona fide organization within the United States, and (C) regularly stationed abroad in such employment, and (2) who is in the United States at the time of naturalization, and (3) who declares before the Attorney General in good faith an intention to take up residence within the United States immediately upon the termination of such employment abroad of the citizen spouse, may be naturalized upon compliance with all the requirements of the naturalization laws, except that no prior residence or specified period of physical presence within the United States or within a State or a district of the Service in the United States or proof thereof shall be required.
The relevant section of the Code of Federal Regulations is 8 CFR 319.2, which says in part:
§ 319.2 Person whose United States citizen spouse is employed abroad.
(a) Eligibility. To be eligible for naturalization under section 319(b) of the Act, the alien spouse of a United States citizen must:
(1) Establish that his or her citizen spouse satisfies the requirements under section 319(b)(1) of the Act, including that he or she is regularly stationed abroad. For purposes of this section, a citizen spouse is regularly stationed abroad if he or she proceeds abroad, for a period of not less than one year, pursuant to an employment contract or orders, and assumes the duties of employment;
(2) At the time of examination on the application for naturalization, be present in the United States pursuant to a lawful admission for permanent residence;
(3) At the time of naturalization, be present in the United States;
(There are three additional requirements but they are not relevant to this question.)
The couple live together outside the US. They apply for immigration of the non-US spouse to the United States. The application is successful and the non-US spouse receives an immigrant visa.
What happens next? How long does it take? In particular, can the naturalization application be submitted before they travel to the US? Can they travel to the US so the spouse becomes a permanent resident and then return to their foreign residence, traveling to the US as necessary for the naturalization interview and for the naturalization ceremony? Consider that the couple want to minimize the time spent in the US because they both work abroad.