What's the meaning of the phrase "The press of his duties meant"?
Though he was an occasional participant in the PDB sessions with President Lincoln, the press of his duties meant that Jason often entered or departed the Oval Office in the middle of a briefing rather than being present throughout.
On first sight, your question might seem answerable by simple reference to a dictionary. But the number of definitions and examples for press offered by Cambridge, Merriam Webster and Collins is surprisingly large, so it is not a trivial task to find meaning, and the question is apt for this site.
In Collins, meaning 45 (!) in the American English section (there are other sections) is:
Collins
press: Noun
pressure or urgency, as of affairs or business
This is the meaning most relevant to your quotation. The pressure and the urgency of Jason’s own affairs and business were so great that he could not give all his time to Oval Office briefings and had to leave them in order to attend to his own business.
Use of press in this way is loosely consistent with the many other examples and meanings, whether as verb or noun. Many of them are associated with pressure, compulsion, strong persuasion, constraint and insistence, whether imposed by circumstance or people.
