After the announcement of the Armistice of Cassibile on 8 September 1943 the regiment was disbanded by invading German forces.

The battalion was based in Trento and assigned to the 4th Alpine Army Corps's Engineer Command.

In 1992, the 51st Engineer Battalion "Simeto" in Palermo lost its autonomy and entered the reformed 4th Pioneer Regiment.

[6][8] The regiment's anniversary falls, as for all engineer units, on 24 June 1918, the last day of the Second Battle of the Piave River.

[8] In July 1935, in preparation for the Second Italo-Ethiopian War, the regiment mobilized the LI Mixed Engineer Battalion for the 32nd Motorized Division "Trento", which was deployed in December 1935 to Libya to deter Great Britain from closing the Suez Canal for Italian shipping.

[8] During World War II the regiment's depot in Bolzano mobilized the following units:[8] On 10 June 1940, the day Italy invaded France, the 9th Engineer Grouping was assigned to the Army of the Po.

On the same day, 10 February 1941, the grouping moved from Verona to Cava dei Tirreni in Campania.

In 1943, the grouping moved to Villa Pergusa near Enna in Sicily, where it was assigned to the 6th Army's Engineer Command.

[10][11][12] On the evening of 17 January 1943, the Alpine Army Corps commander, General Gabriele Nasci, ordered a full retreat.

The 40,000-strong mass of stragglers — Alpini and Italians from other commands, plus German and Hungarians — followed the "Tridentina" division, which led the way westwards to the new Axis lines.

The retreat through the frozen steppe and constant skirmishes with Soviet forces decimated the Alpine Army Corps, which barely escaped annihilation during the Battle of Nikolayevka.

In late January 1943, the remnants of the Alpine Army Corps reached Axis lines and in March the few survivors were repatriated.

[1][10][11][12] In the evening of 8 September 1943, the Armistice of Cassibile, which ended hostilities between the Kingdom of Italy and the Anglo-American Allies, was announced by General Dwight D. Eisenhower on Radio Algiers and by Marshal Pietro Badoglio on Italian radio.

Germany reacted by invading Italy and the 4th Engineer Regiment was disbanded soon thereafter by German forces.

[6][8][13] On 12 November 1976, the President of the Italian Republic Giovanni Leone assigned with decree 846 the flag and traditions of the 4th Engineer Regiment to the battalion.

After the 1980 Irpinia earthquake, the battalion was deployed to southern Italy for the rescue efforts.

[8] In 2001 and 2002, the regiment was deployed to provide heavy military engineering equipment during the eruptions of Mount Etna and Stromboli.