You are only as strong as your weakest link, and for Ukraine, that link is fast becoming the United States.  The Biden administration continues to balk at Ukraine’s request to strike, at will, military targets within Russia that pose a “clear and imminent threat” to the Ukrainian Armed Forces and civilian population centers. Red lines have become a Washington and Brussels problem, not one for Ukrainian President Volodymyr Zelensky and his generals. Determined to drive the Russian invader from Ukraine and win the war, Ukraine has taken the fight to Russian soil. To achieve his aims, Zelensky has increasingly turned to his own country’s resources with remarkable success. He has also boldly taken the initiative by invading the Kursk Oblast in southwestern Russia, to the chagrin of many. Zelensky’s inner circle, including Gen. Valery Zaluzhny, the former commander who is now Ukraine’s ambassador in London, cautioned against it. Emil Ishkulov was relieved as the commander of Ukraine's 80th Air Assault Brigade after he opposed Zelensky’s Kursk offensive attack. President Biden’s own risk-averse national security advisors, including Jake Sullivan, Secretary of State Antony Blinken and Secretary of Defense Lloyd Austin, were aghast. They likely viewed Kursk as a red line as well.  Yet the Ukrainian military continues to expand its foothold in Kursk. Ukrainian Gen. Oleksandr Syrskyi estimates that Ukraine now controls 1,000 square kilometers of Russian territory.  This has forced the Kremlin to reposition forces to counter the intrusion, providing some relief for Ukrainian defenders in the Donbas and Pokrovsk.  Maneuver, however, is not a Russian strength. As the Kremlin’s forces reposition, their convoys have presented lucrative targets for the Ukrainian artillery and attack drones. It has been a turkey shoot on the Russian highways and railways leading to Kursk.  For now, Russian President Vladimir Putin remains undaunted. His forces continue to advance in the Donbas. And as they advance, their losses have risen to 1,000 a day. An astounding 70,000 were killed or wounded between May and June, and 645,150 since February 2022.  Putin appears determined to continue feeding the Ukrainian meat grinder. On September 16, he signed a decree increasing the overall number of soldiers in the Russian military by 180,000. Zelensky had an immediate response. Two days later he went for the Russian army’s center of gravity: artillery via its munitions pipeline. Ukrainian-manufactured drones struck an ammunition depot in the Tver region of Russia. The depot, located in the town of Toropets, is approximately 240 miles west of Moscow and 300 miles from the Ukrainian border.  The depot held Iskander tactical missiles, Tochka-U missile systems, glide bombs, air defense missiles (S-300 and S-400), Grad multiple launch rocket systems and artillery ammunition. According to a Ukrainian Defense Ministry official, it also contained North Korean KN-23 ballistic missiles, which have been used to target and kill Ukrainian civilians. The Toropets explosion and its surge in thermal activity was captured by NASA satellites. An estimated 750,000 shells were destroyed, or the equivalent of two to three months' supply for Russian forces. Biden should be taking notes: Interdiction is a good thing. The Patriot missile system, National Advanced Surface-to-Air Missile System and all the other air defense assets provided to Ukraine are essential. But destroying these munitions in Russian ammunition depots is a far better strategic course of action. Adding insult to injury, an image of Ukraine’s intelligence chief, Kyrylo Budanov, appeared on the Toropetsk District’s web page shortly after the attack. Zelensky is putting to work the "I" in DIME (information). The drone strike was followed by strikes on ammunition depots in Tikhoretsk and Oktyabrsky. The Tikhoretsk ammunition depot is one of the three largest in Russia. The Oktyabrsky arsenal is the Main Artillery Directorate. Reports suggest a supply train delivering at least 2,000 tons of ammunition, including North Korean ballistic missiles, was at the facility. Innovation, ingenuity and resourcefulness in the form of domestic weapons has afforded Ukraine some of the operational reach it needs to interdict Russia’s ability to strike Ukrainian population centers. Ukraine has demonstrated that hitting those targets deep within the Russian interior is well within its capabilities and intent.  A revamped Neptune missile and the new Palianytsia missile/rocket-drone have become Ukraine' s deep strike weapons of choice. The strike on the Toropetsk ammunition depot easily exceeded the range of ATACMS (190 miles); British Storm Shadow and French SCALP air-launched cruise missiles each have a range of just 155 miles. But it is not just ammunition depots they are striking — Ukraine has struck Russian air bases, seaports, oil refineries, assembly plants, and government facilities throughout the Russian interior. Putin does not like this. On Sept. 12, he warned the U.S. and NATO that he would consider the approval of plans to allow Kyiv to strike targets inside Russia with Western-supplied missiles tantamount to NATO directly entering the war stating, “This will mean that NATO countries, the United States, and European countries are fighting Russia.”  Even so, he does not seem to have any problem with firing North Korean and Iranian ballistic missiles into the interior of Ukraine. Kremlin spokesperson Dmitry Peskov added that Russia’s response “will be appropriate,” implying once again a nuclear option. That threat lost a bit of its luster on September 21, when a Russian RS-28 Sarmat intercontinental ballistic missile test launch — timed to demonstrate Russian nuclear capability — suffered a “catastrophic failure” on the launch pad at Russia's Plesetsk test site. Yet Biden had already caved. White House national security spokesman John Kirby explained, "There is no change to our view on the provision of long-range strike capabilities for Ukraine to use inside Russia, and I wouldn't expect any sort of major announcement in that regard coming out of the discussions — certainly not from our side." Zelensky is back in New York City. He briefed the U.N. General Assembly on Sept. 20, urging the country's representatives to come together against Russian aggression, stressing the need for peace, and recognizing Ukraine’s territorial integrity. Later today, he will present his victory plan to Biden. Ukraine cannot win this war without the ability to interdict Russian forces and their equipment before they arrive on the battlefield in Ukraine and to disrupt Russia’s war machine from afar using ballistic missiles and glide bombs.  Even if Ukraine kills or wounds 1,000 Russian soldiers a day in Ukraine, this has no impact on the war if Russia can simply reset the next day. Ukraine must be able to stop the flow, and precision deep strike weapons provide that capability.  The war simply cannot be contained inside the borders of Ukraine. The Ukrainian military cannot defend its way to victory. Zelensky has a workable, winnable plan to take the fight to Russia, but it requires American backbone. Col. (Ret.) Jonathan Sweet served 30 years as an Army military intelligence officer. Mark Toth writes on national security and foreign policy.