It will take about three months to get new D-9s. It takes the same amount of time to get the armor kit. The army is also looking into getting some D-9s more quickly from civilian firms (lease or purchase). The Army wants these vehicles in a real hurry, as if they were going to be needed before the end of the year. The U.S. Army has some smaller (30 ton) D-7 bulldozers, also equipped with armor, but these are meant for mine clearing, not plowing through buildings in support of street fighting.
Army engineers were rather amused with all this hustle to get D-9s, as they have long wanted to build the Grizzly CEV (Combat Engineer Vehicle). The Grizzly is based on the M-1 tank chassis, adding a large bulldozer blade and a special turret. The army wanted to buy nearly 400 of them, and have them enter service in 2003, but the project is on hold so the money can be used for the new Medium Brigades and other new ideas. Some of the Grizzly prototypes are being readied for possible combat. The Grizzly is better armored and has more equipment and weapons on it. While the D-9 would be in big trouble if enemy tanks or heavy anti-tank weapons (missiles or guns) were around, the Grizzly would not be. But the Grizzly's cost several million dollars each and cannot be obtained quickly.
The existing 1960s era M728 CEV are unavailable (lack of spare parts and qualified mechanics) and unsuitable (it uses a tank transmission that cannot gear down low enough to knock things down like the D-9 can). Vehicles like the D-9 (which is a real beast, although the D-10, at 60 tons, is even meaner looking) are superior to a recycled tank for demolition duties. Moreover, you have the "combat proven" aspect. This is a big thing, and the army can send engineers to Israel to get trained by troops who have used the D-9 in combat.
Impressed with the Israeli use of heavy Caterpillar D-9 bulldozers (nicknamed "The Beast" by Israelis and Palestinians) in West Bank street fighting, the U.S. Army has ordered a dozen D-9s. These 52 ton tracked vehicles cost half a million dollars each. The army will equip them with Israeli made armor kits at a cost of $120,000 per vehicle (and several tons of additional weight). Total cost of this purchase, including installation and shipping, will be about $8 million. The D-9, configured for combat, can crash right through smaller buildings, and into larger ones. Roadblocks can be quickly cleared and rubble can be rapidly moved about. The engine makes a fearsome noise (thus the nickname), just the sort of roar you'd expect from an instrument of destruction. The Israelis found that the psychological effect of seeing and hearing "The Beast" approaching often caused enemy fighters to flee. The U.S. Army used D-9s during the Vietnam war to knock down jungle (and eliminate hiding places for enemy troops along roads and around friendly bases.) But after the war, the D-9s were sold off.