I understand that people in this forum either seeks to diminish US accomplishment or ride the coattails of the same, but the reality is that absolutely %100 of the credit for the development of low radar observability platforms belongs to the US.
It is not correct definition.
The US always targeted "air invulnerability".
First it was the height, after that the speed, finally the low observability.
The CCCP strategical direction was different from the beginning, they wanted to protect own country / area.
Due to that the type of aircraft that the US riding at the moment never was a priority for the CCCP.
Ufimtsev developed his methods to design better radards for air defence systems : )
US military doctrine is to be capable to attack any country any time, and to be able to bomb back to the stone age the civilian infrastructure and to kill enough civilian to force the country to accept the US conditions.