US extended deterrence guarantees to its allies in Europe, the Middle East, and East Asia can best be described as a mixed bag. Over the years, different US administrations have adopted varying policies to protect allies from nuclear attack as part of the country's extended nuclear guarantees. However, these policies do not follow in a linear fashion. Measures taken by the Obama and Trump administrations have had differing impacts on different sets of allies, often with the same move eliciting trust from one set while contributing to diminishing trust in another.

This paper looks at what constitutes the ‘trust’ of allies under the US nuclear umbrella, and what parameters are considered pre-requisites for continued US extended nuclear deterrence guarantees. Trust in extended nuclear deterrence guarantees is contingent upon on two important factors:

1. Continuing shared interests and a common threat perception between the country extending the nuclear security guarantees and the country(s) receiving them

2. Policy continuity over different US administrations in extended deterrence guarantees.

An absence of either of these factors can lead to a faltering of trust in extended deterrence. Against this background, this paper analyses the changes that have come about in US extended deterrence, especially in the nuclear umbrella, from the Obama years to the current Trump dispensation, by taking into consideration Europe, East Asia, and the Middle East.