In article ,
Mike Walsh wrote:
Command guidance was regarded as undesirable because of vulnerability to
enemy countermeasures...

Also because the launch site needed an elaborate set of radars which were
virtually impossible to harden against attack in any meaningful way, and
could be used for only one launch at a time. Almost any credible scenario
for *using* the things required either rapid-fire multiple launch or the
ability to ride out attacks, so command guidance just did not make much
sense for large-scale deployment.

One of the biggest advances in target accuracy was achieving more accurate
mapping. If you don't know where you really are at the launch point and
don't know exactly where the target is...

In particular, apparently there was some unhappiness when people realized
that the relative locations of the *continents* were not known accurately
enough for ICBM targeting. Within a continent it was possible to do quite
accurate surveying with aerial photos and the like, but accurately
determining the precise distance between North America and Eurasia was not
so simple, and some effort had to be made in a hurry.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |