wintering said:
I'm a bit unsure as to how the geopolitical developments - vietnam, sino-soviet split, and the middle east - affected detente? that is, positively or negatively?
Look at to what extent geopolitical events led to detente. The USA and USSR each had different reasons for detente, both policical and economic. You'd need to look at each for both sides.
Eg: Vietnam. USA economy going into recession, massive military spending, unpopular war at home, elections looming for Nixon. Wanted 'peace with honour'.
Sino-Soviet split. Different ideas on communism. Nixon visits Beijing and this impacts on the USSR - they don't want the USA being cozy with the Chinese. USA exploit this.
good luck!