When Russia invaded Ukraine on February 24, many US national security officials and analysts predicted that Ukraine’s military would be able to hold out for only a few days, if not a week.

However, Russia’s invasion of Ukraine has stalled six months later, as Russia’s military capabilities have fallen far short of what they appeared on paper, and Ukraine’s military, bolstered by a constant supply of weapons from the US and the rest of the international community, has demonstrated its willingness to fight hard in every part of the country.

ABC News spoke with national security experts and a senior British military officer about how the battle in Ukraine has evolved over the last six months and what might happen next. When Russian troops invaded Ukraine simultaneously on multiple fronts in February, it appeared to be an attempt to quickly overwhelm Ukraine’s military.

However, six weeks later, the combined effects of Russia’s poor military decisions and planning resulted in the tactical withdrawal of its forces stalled north of the capital Kyiv and a shift eastward to the Donbass region.

Months of intense artillery barrages and rising casualties have resulted in only minor territorial gains for Russian troops, and as Ukraine prepares for a counteroffensive in southern Ukraine, the fight has already shifted there.

And it has come at a high price for both Russia and Ukraine. The US believes Russia has lost between 70,000 and 80,000 soldiers and civilians, and Ukrainian President Volodymyr Zelensky acknowledged in June that his forces were losing 60 to 100 soldiers every day.

According to O’Hanlon, there may be a lull in fighting in Ukraine this winter as both sides rebuild their forces for a fight next year, similar to what happened during World War I.

According to retired US Army Lt. Gen. Ben Hodges, an adviser with Human Rights First, Russia has entered an attrition war that it may not win. As the top Army officer in Europe, Hodges developed the U.S. military training program for Ukraine’s security forces following Russia’s 2014 invasion of Crimea.

“If you’re going to do attrition, you need three things: a large number of people, a large number of resources, and a large amount of time. And the Russians lack all three of them “Hodges stated. “So, unfortunately for them, they’ve chosen the wrong strategy to defeat Ukraine.”

Hodges believes Russia’s logistical supply network has been stretched to its breaking point and will be unable to supply Russian troops in the long run, and he is skeptical that the Russian people will continue to support the invasion as time passes.

Air Vice Marshal Mick Smeath, the defense attaché at the British embassy in Washington, is more cautious about what he says. Smeath is confident that the flow of Western military aid to Ukraine will continue for the foreseeable future.

Given their vast arsenal of weapons, recent modernization efforts, and a shift toward a more professional force rather than relying solely on conscripts, Russia’s military was expected to quickly overwhelm Ukraine. However, the last six months of conflict in Ukraine have exposed Russia’s military capabilities and left them significantly weakened, as its battalion tactical groups have consistently suffered heavy casualties.

Russia’s recent military modernization effort centered on integrating its warfighting capability across land, sea, and cyberspace.

At that point, O’Hanlon emphasized Russian plans to drive heavy military vehicles across fields that were not as frozen as expected, causing bottlenecks on roads and exposing them to attacks by Ukrainian fighters.

While Russia’s poor performance on the battlefield was unexpected, O’Hanlon noted that there were indicators that it could happen given that “we haven’t seen the Russians fight well on a large scale in a very long time.”