The end of WW2 and the early Cold War years saw the need for a more powerful tank than the Sherman and Pershing tanks.
Never.
The original M48 had serious deficiencies.
As the Cold War intensified, the M47 went into mass production and countered the Soviet build up.
The first Patton tanks (M46) were converted Pershings which saw service in Korea.
The end of WW2 and the early Cold War years saw the need for a more powerful tank than the Sherman and Pershing tanks