The Israel-Hamas war, particularly if it continues into 2024 or grows into a regional war, will likely reduce Ukraine's ability to resist Russia's invasion by increasing competition for funding and key weapons systems in the West and particularly the United States, which will in turn force Kyiv to adopt a more passive strategy to preserve its resources for the long run. In an Oct. 19 address aimed at rallying congressional and public support for his approach to the ongoing conflicts in Israel and Ukraine, U.S. President Joe Biden argued that curtailing support for either of the countries would be much more dangerous and costly for the United States in the long run. Biden said he would send an ''urgent budget request'' to Congress, referring to a reported $100 billion bill that would include around $60 billion for Ukraine and approximately $10 billion for Israel, as well as for aid to nations in the Indo-Pacific. However, just hours before Biden's speech, Axios published a report detailing U.S. Pentagon plans to supply Israel with tens of thousands of 155mm artillery shells that had been originally designated for Ukraine from U.S. emergency stocks, citing three Israeli military sources with knowledge of the matter. While Biden's address and funding request will eventually result in further crucial mid-term support funding for Kyiv, such reports that Israel now needs resources earmarked for Ukraine — combined with concerns about the size of Biden's bill and how long its funding is expected to last — will add to the growing perception in the Congress that the United States does not have enough resources to simultaneously support Ukraine and Israel's defense without jeopardizing Washington's other commitments. And as a result, Kyiv will likely receive less military aid and other forms of U.S. support in the coming months than it otherwise would have, had Israel not become engulfed in another conflict against Palestinian militants, and the subsequent deepening of political infighting over military support in Congress.

• Instability in the Middle East amid the Israel-Hamas war has already prompted the United States to reposition an amphibious task force of over 4,000 Marines and sailors to the region, with another 2,000 support troops placed on alert and told to be ready for deployment within days. This reflects Washington's attempts to deter escalation of the conflict and accelerate its preparations for contingencies involving an expansion of the war. 
• The U.S. Congress passed a stopgap funding bill late on Sept. 30 that lasts through Nov. 17 but does not include funding for military aid for Ukraine. On Oct. 2, U.S. House Speaker Kevin McCarthy was removed, and the chamber's subsequent failure to find a replacement and return to business has called into question Congress' ability to pass a short-term Ukraine support funding package before the looming government shutdown, let alone the large bill proposed by Biden in his speech. 
• The question of whether the United States should continue to support Ukraine's resistance against Russia's invasion is arguably the most divisive issue within the U.S. Republican Party at this time. Rep. Matt Gaetz, the congressman who initiated the motion that ousted McCarthy, cited a ''secret deal'' that McCarthy allegedly struck with the White House on a supplemental Ukraine support funding bill as one of the justifications for his removal. Gaetz is the most prominent proponent in Congress of ending all military aid to Ukraine, having authored an amendment to defense funding bills that would prohibit all military assistance to Ukraine. 93 Republicans in the House of Representatives supported the amendment in a Sept. 28 vote, up from 70 who voted for a similar measure he put forward in July.

The war in Gaza will increase competition for funding and specific military equipment, such as artillery ammunition and precision munitions, jeopardizing Ukraine's ability to fight in the near term by leaving fewer resources for Kyiv. Ukraine and Israel's militaries both use multiple U.S. and Western weapons systems and ammunition that each needs to sustain their operations against Russian troops and Hamas militants, respectively. The most important of these are NATO-standard 155 mm caliber artillery ammunition, which Ukraine has steadily transitioned to following Russia's 2022 invasion and which Israel is already using as part of its shelling in preparation for a potential ground invasion of Gaza. In fact, earlier this year, the United States began supplying Ukraine with U.S. 155mm artillery ammunition stored in Israel, leading to low stocks in the Middle Eastern country. This likely played a role in Israel's August 2023 decision to place a new order with domestic arms producer Elbit for tens of thousands of 155mm artillery shells. Though Israel does not need nearly as much artillery as Ukraine, Elbit is highly unlikely to ramp up production quickly enough to prevent Israel from drawing deep into stockpiles. Artillery ammunition is arguably the most important resource for Ukraine's ability to hold its ground against Russia and continue counter-offensives. Any disruptions to its steady supply as a result of the Gaza conflict will thus have an adverse effect on Kyiv's position on the battlefield by making it unlikely to possess a daily artillery usage advantage in the coming months, instead having to rebuild its supplies to enjoy a temporary advantage in a future offensive. However, the overlap between Israel's and Ukraine's military equipment demands likely also extends well beyond artillery ammunition to other munitions — such as mortar ammunition, precision munitions such as Hellfire missiles and a host of nonlethal support systems — which could bode poorly for the future availability of these U.S. systems for Kyiv. 

• According to the Pentagon, the United States has provided over 2 million artillery shells to Ukraine since the start of Russia's invasion in February 2022, but these deliveries only enabled Ukraine to approach Russian troops' daily usage during Kyiv's offensive in recent months. Ukraine is also currently firing shells at an unsustainable rate, faster than its Western allies are willing to replenish without dipping too deep into their own stocks; the West remains years away from reaching its new monthly production targets as well. 
• The United States plans to increase its monthly production of 155-millimeter artillery shells to only 100,000 by 2025, up from the estimated 28,000 shells it currently produces each month (and the 14,000 shells it was producing monthly at the start of 2023). In September, the CEO of the German defense and industrial giant Rheinmetall estimated that the Ukrainian military needs at least 1.5 million artillery shells each year to maintain a usage rate necessary to continue resisting Russia's invasion. 

If the Israel-Hamas war drags on and/or grows into a regional war, it will further distract Western policymakers from the war in Ukraine and embolden voices in the U.S. Congress who want to reduce support to Kyiv. Israeli officials, including Prime Minister Benjamin Netanyahu, have repeatedly warned of a ''long war'' with Hamas, as well as the possibility of the conflict's expansion beyond the Gaza Strip to the West Bank and Israeli-Lebanese border. Additionally, a series of Iranian warnings indicate a growing risk of the Israel-Hamas war growing beyond its current geographic scope, a prospect that Israel and the United States — along with other regional and Western powers — are likely being forced to prepare for, including in regards to their military procurement. The latest Israel-Hamas war is currently expected to only last a few more weeks. But if conflict endures for longer, and particularly if it begins spilling into other nearby countries, it will very likely strain U.S. military supplies and, in turn, hinder Ukraine's ability to receive munitions. Additionally, a prolonged and/or expanded Gaza conflict would likely reduce support in the U.S. Congress for continued deliveries to Ukraine by convincing more lawmakers in the Republican-controlled House of Representatives to cut back on support for Ukraine in favor of Israel and other priorities. To overcome this challenge, the White House appears open to the idea of linking four previously separate issues: support for Ukraine, Israel, Taiwan and other Asia-Pacific partners, and border security funding. This strategy will give the Biden administration flexibility and may be politically necessary in the short- to mid-term to overcome Republican opposition in Congress. But in the long run, it will almost certainly result in less military support for Ukraine by putting such aid in direct competition with other initiatives that enjoy somewhat higher levels of congressional approval, particularly among Republicans. Lower levels of U.S. support will further reduce the Ukrainian military's already limited ability to retake the territory that Russia has seized over the course of its invasion, forcing Ukraine to adopt a more conservative strategy that hinges on passively waiting for political change in Russia to increase its chances at victory, rather than forcing such change via advances on the battlefield that degrade Russian forces and President Vladimir Putin's hold on power.