On September 19th the White House received the following intelligence estimate on the “military build up in Cuba”. This paper speculated that the installation of ballistic missiles in Cuba was unlikely:
“We believe that the USSR values its position in Cuba primarily for the political advantages to be derived from it, and consequently that the main purpose of the present military buildup in Cuba is to strengthen the Communist regime there against what the Cubans and the Soviets conceive to be a danger that the US may attempt, by one means or another, to overthrow it.
The Soviets evidently hope to deter any such attempt by enhancing Castro’s defensive capabilities and by threatening Soviet military retaliation. At the same time, they evidently recognise that the development of an offensive military base in Cuba might provoke US military intervention and thus defeat their present purpose.
In terms of military significance, the current Soviet deliveries are substantially improving air defence and coastal defence capabilities in Cuba. Their political significance is that… they are likely to be regarded as ensuring the continuation of the Castro regime in power, with consequent discouragement to the opposition at home and in exile. The threat inherent in these developments is that, to the extent that the Castro regime thereby gains a sense of security at home, it will be emboldened to become more aggressive in fomenting revolutionary activity in Latin America.
As the buildup continues, the USSR may be tempted to establish in Cuba other weapons represented to be defensive in purpose but of a more “offensive” character, eg. light bombers, submarines, and additional types of short range surface to surface missiles (SSMs). A decision to provide such weapons will continue to depend heavily on the Soviet estimate as to whether they could be introduced without provoking a US military reaction.
The USSR could derive considerable military advantage from the establishment of Soviet medium and intermediate range ballistic missiles in Cuba, or from the establishment of a Soviet submarine base there. As between these two, the establishment of a submarine base would be the more likely. Either development, however, would be incompatible with Soviet practice to date and with Soviet policy as we presently estimate it. It would indicate a far greater willingness to increase the level of risk in US-Soviet relations than the USSR has displayed thus far and consequently would have important policy implications with respect to other areas and other problems in East-West relations…”